Advice on crossmembers, column, shifter for new engine and trans swap

[rechinca]

I was not really planning on going this route as I have loved the coolness factor of running my 350 basic crate engine with the 3 on the tree. It has been a blast, but an opportunity came up I felt I couldn't resist. A complete 383 roller cam BluePrint Engines with a full Holley front runner and all the accessories, MSD distributor, PowerMaster starter radiator and electric fans. I know what was invested in the combo and with 500 miles on it, I got it for half of what was invested in it.

I'll need headers, trans crossmember, probably change the trailing arm crossmember, new column and a decision of going with a sniper or just running a Holley carb since that is what it came with. This truck is a factory V8 with 3OTT so I understand I will need to make some changes. Initial thought is to go with a Gearstar automatic trans.

This was not a thought out purchase, just a stupid good deal that I could not pass up. It was going in this winter to finish the rust repair on the cab and new main wiring harness so this might be a bit more involved. I have already been reading up on everything, but new perspectives and advice on what you used and did or didn't work will be appreciated. Guess the open 12 bolt with 3.08 gears is going to need some upgrades too.

[Palf70Step]

I am in the process of doing the same now. Due to medical stuff, I'll be retiring my 3 OTT sooner then I planned. I have a T350 transmission. I just got a automatic column. Digging up the trans crossmember, column linkages, make some lines and trans cooler to do the change out. I also have a peg leg 3.08 rear. It should do fine, unless you really want to stomp on that engine alot. Mine is just a cruiser niw so I know I am OK. Good luck with yours.

[rechinca]

Originally Posted by Palf70Step

I am in the process of doing the same now. Due to medical stuff, I'll be retiring my 3 OTT sooner then I planned. I have a T350 transmission. I just got a automatic column. Digging up the trans crossmember, column linkages, make some lines and trans cooler to do the change out. I also have a peg leg 3.08 rear. It should do fine, unless you really want to stomp on that engine alot. Mine is just a cruiser niw so I know I am OK. Good luck with yours.

I absolutely loved the 3OTT and it was one of the main reasons I bought this truck. But I'll be honest sitting in traffic means I never drive it to work. I look forward to converting it, but I will definitely be going with an overdrive.

[Duncan_s]

Originally Posted by rechinca

I was not really planning on going this route as I have loved the coolness factor of running my 350 basic crate engine with the 3 on the tree. It has been a blast, but an opportunity came up I felt I couldn't resist. A complete 383 roller cam BluePrint Engines with a full Holley front runner and all the accessories, MSD distributor, PowerMaster starter radiator and electric fans. I know what was invested in the combo and with 500 miles on it, I got it for half of what was invested in it.

I'll need headers, trans crossmember, probably change the trailing arm crossmember, new column and a decision of going with a sniper or just running a Holley carb since that is what it came with. This truck is a factory V8 with 3OTT so I understand I will need to make some changes. Initial thought is to go with a Gearstar automatic trans.

This was not a thought out purchase, just a stupid good deal that I could not pass up. It was going in this winter to finish the rust repair on the cab and new main wiring harness so this might be a bit more involved. I have already been reading up on everything, but new perspectives and advice on what you used and did or didn't work will be appreciated. Guess the open 12 bolt with 3.08 gears is going to need some upgrades too.

Good deal, Sounds like you found a good powerplant at a great price! My truck was a 3 on the tree as well. ive grown tired of it and made the swap to a tkx. Im planing on just punching out the roll pin on the shifter handle and running the same column. these trucks came with turbo 350s from the factory, i dont exactly know what transmissions youre going with id imagine you could modify a turbo 350 crossmember to work. considering the popularity of these trucks cant imagine a whole kit to put an auto wouldnt be hard to find. One thing i would be make sure to watch out for is your 3.08 rear end. its a good rear end to run and they hold up to abuse pretty well, and posi units can be bought for it. but i would be careful on the fact that it is a SERIES 3 carrier not a 4. factory 3.73 and higher rear ends were a series 4 carrier not a 3. distinct difference and a 4 cant go into a 3. You can buy a series 3 3.73 ring and pinion plus a posi unit and swap that into your rear end. my truck is a factory 3.08 posi unit, i am changing out the ring and pinion to 3.73's. Good luck!

[HalfBrit]

My '70 was an original 307 / 3.73 / 3 OTT truck. I swapped a 350 and a M21 and stayed with the bellhousing crossmember (no trans mount). Does your truck have that crossmember? Correct me if I'm wrong, but if you go automatic, wouldn't you also need to remove that to be able to install a "regular" transmission crossmember? Dirty Dingo makes a nice crossmember with height adjustability (for fine tuning driveline angles) and exhaust clearance, for lowered trucks. Here's a link:
https://www.ebay.com/itm/17297035555...YaAh_AEALw_wcB

[LS short box]

My 68 had a 3 OTT. When I swapped in an LS engine I scrapped the stock column and went with an Ididit tilt column. Worked great. Also used an aftermarket steering wheel smaller in diameter than stock for a bit more elbow room.
Pic.

[rechinca]

Originally Posted by Duncan_s

Good deal, Sounds like you found a good powerplant at a great price! My truck was a 3 on the tree as well. ive grown tired of it and made the swap to a tkx. Im planing on just punching out the roll pin on the shifter handle and running the same column. these trucks came with turbo 350s from the factory, i dont exactly know what transmissions youre going with id imagine you could modify a turbo 350 crossmember to work. considering the popularity of these trucks cant imagine a whole kit to put an auto wouldnt be hard to find. One thing i would be make sure to watch out for is your 3.08 rear end. its a good rear end to run and they hold up to abuse pretty well, and posi units can be bought for it. but i would be careful on the fact that it is a SERIES 3 carrier not a 4. factory 3.73 and higher rear ends were a series 4 carrier not a 3. distinct difference and a 4 cant go into a 3. You can buy a series 3 3.73 ring and pinion plus a posi unit and swap that into your rear end. my truck is a factory 3.08 posi unit, i am changing out the ring and pinion to 3.73's. Good luck!

Yeah the jury has been out on mine, as it’s not the original rear end. Someone swapped in a leaf spring style 12-bolt (no ear on the top of the housing for the track bar) and I can’t find the stamping for more info on it. Since it worked I haven’t paid attention to guts when I changed the fluid other than to get the ring gear info.

[RustyPile]

All the posters have addressed your issues except one.. In your first post, you mentioned probably change the trailing arm crossmember.. There's no reason to change it even if you now have leaf springs in the rear.. If the trailing arms have been removed and your truck is long wheel base, you'll need the cross member to mount the center support bearing for the driveshaft.. If it's not needed for that, leave it in place anyway as it adds a great deal of stiffness to the frame..

[rechinca]

Originally Posted by RustyPile

All the posters have addressed your issues except one.. In your first post, you mentioned probably change the trailing arm crossmember.. There's no reason to change it even if you now have leaf springs in the rear.. If the trailing arms have been removed and your truck is long wheel base, you'll need the cross member to mount the center support bearing for the driveshaft.. If it's not needed for that, leave it in place anyway as it adds a great deal of stiffness to the frame..

Still a trailing arm suspension so I am not removing, looking to clean up a bit by changing it instead of just changing the trailing arm mounts on it.

[rechinca]

I was able to run out and pick up the new to me powerplant over this last weekend. Who says you can't haul a load with a lowered LB? 5" Spring drop in the rear with no C-Notch (at least not yet), threw in the cherry picker, loaded the new engine and extras and back home.

[rechinca]

Originally Posted by HalfBrit

My '70 was an original 307 / 3.73 / 3 OTT truck. I swapped a 350 and a M21 and stayed with the bellhousing crossmember (no trans mount). Does your truck have that crossmember? Correct me if I'm wrong, but if you go automatic, wouldn't you also need to remove that to be able to install a "regular" transmission crossmember? Dirty Dingo makes a nice crossmember with height adjustability (for fine tuning driveline angles) and exhaust clearance, for lowered trucks. Here's a link:
https://www.ebay.com/itm/17297035555...YaAh_AEALw_wcB

Yep, same here with still having the bellhousing mount for the 3OTT. I know that will have to go. I have found a couple of aftermarket ones that seem to look the part and claim to bolt in to the factory holes in the frame. Guess my first real decision is the trans. Really leaning toward the 700r4 to get the OD and then I have to pick a vendor. Going to try and get over to my local trans shop first though next week. Old school guy who has done work on a couple of my vehicles so far and I trust to build me one. I'd like to pick his brain and see what he has for input.