71 C10 454 Engine Swap Info needed

[Hack71]

I'm preparing for an engine swap on my 71 C10 Cheyenne long box. The truck is an original 350/TH350 with factory A/C, PS, PB, I will be swapping in a 454/TH400 from a motorhome. I want to be as prepared as possible. I've searched some posts and got some conflicting info. I want to do a budget friendly swap; my biggest concern is how the 454 will sit in the engine bay. I've heard that it depends on which engine frame mounts I use, I would like to use clam style engine mounts and frame towers from a 73 and newer, does it matter if they are from a c10, c20, c30, does it matter if they are from a SBC or a BBC, I've read that the engine could sit to far back on the firewall. I have the transmission yoke for the TH400, Will the 454/400 swap in without changing the length of the driveshaft? Currently I have a two-piece shaft. Will the trans crossmember need to be moved? my plan is to use a 19" electric fan from a Jeep Cherokee and mount it in the 71's original fan shroud. the truck has a 4-row radiator that should be sufficient. Pics are attached, any advice or info would be greatly appreciated. Thanks,

[D.B]

Keep in mind the TH400 has an electric kickdown and the TH350 is cable driven from the carb.

[notsolo]

Beautiful truck, 3 tailshafts also for the 400. Probably need driveshaft cut, I cut 3" off mine for a 4L60 swap, engine to the rear position... I think the claim shells are all the same, frame mounts different for some applications. Save the power steering big nut, flare adapter from your old setup.

[Hack71]

Thanks, any thoughts on retaining the TH350 behind the 454, the 454 has a mild cam, its not pushing a lot HP or torque. The TH350 is solid with a shift kit

[71meangreenc10]

I would not use the Jeep fan with the 454. Get a Big Block fan shroud and use a newer HD fan clutch for reverse rotation with a fan (I have a pic) and put a pusher fan on the condenser. If the TH350 is built, use it. As long as the mounts are in the V8 position you should be fine. If you put them in the 6 cyl location the HEI will hit the fire wall. Most people who convert 6cyls to 8's do not put forth the effort to move everything into the factory location and that is why you see stuff riding the firewall.

I have used the Jeep fan mod in the past.

Smitty

[HO455]

I have a destroked 455 Pontiac that has dynoed over 450 hp on several different chassis dynos and has run 11.20's at over 120 mph in a 3400 pound GTO bolted to a T350. It was properly built for this an has a 10 inch Continental converter that stalls around 2800. It's been a great transmission for over 10,000 miles.
So yes, T350's will get the job done with the proper preparation. Now towing may change the viability of a T350.

[shortbedmike]

your th400 will require a bolt in high hump tunnel and a little cutting, and then a new carpet for the high hump. if you stay with the th350 check the flex plate for the th350 bolt patern, a lot of the motor home used 6 bolt converters and the flex plate won't have a dual pattern. so you may need to buy a new one as the 454 is external balanced so the one on you small block won't work.

[lolcopter]

I used the clamshell mounts. I have a 700r4 and had to slide the trans cross member back and shorten driveshaft. Photo to show how it sits in engine bay.