Big Blue 1975 C30 --> K30 Conversion and other Upgrades.

[Honest Bob]

I am starting a thread here to document the combination of two trucks into one.

Truck #1 A blue and white 1975 GMC C35 Sierra Grande 2wd/1ton, 350/TH400 86k miles. Saved from being crushed at the junk yard.

Truck # 2 The Rat a 1977 GMC K20. 4x4 3/4 ton, 4.8 LS swapped (Comp X260 cam, ls6 valve springs, headers), turbo 350.

[Honest Bob]

The body on truck #1 is really solid for a 75 where I live but its 2wd.

Truck #2 is not solid in any way the bed is barely held on, cab supports are ready to crumble, frame is really rough behind the cab, hood is rusted and cracked by the hood latch, and one fender might be ok and the turbo 350 has 4 neutrals. Despite the bad its got some good parts in it.

[Honest Bob]

The goal is to combine the best stuff from each truck onto this CUCV frame. I've never attempted any project this large before, I've done alot of research but still have alot more to go.

I'm going to start with getting the frame rolling. I'm going to make a list here to keep things organized.

1. Verify Gear ratio's on all three axles. I'm hoping I can use the rear from the 2wd so I dont have to move spring perches and I can keep the big rear brakes. Blue has 4.10's Rat has 3.21's (I guess that's why it got so much better gas mileage!)

2. See if I can use the 2wd JB8 front calipers on the 10 bolt.

3. See if I can reuse the Rat's old ubolts. Yeah right!

4. Order ORD bolt in steering brace.

[Honest Bob]

Upon disassembly I found out that the input shaft on the 205 is what broke. The gearing mixed with the larger diameter tires was most likely the culprit.

Here is a vido of the rat on the dyno making 270whp and 291wtq.
https://www.youtube.com/watch?v=UYXwG8lXc1Y

My brother in law helped me remove the trans and motor, there isnt a whole lot more I need to pull, just exhaust gas tank and other small misc items.

[Honest Bob]

Some shots of the parts truck, you can see why it was a parts truck.

[Honest Bob]

The Rat is gone!

https://www.youtube.com/watch?v=aOkxCn0BqZM


Picked up a 10 Bolt off of the classifieds and started cleaning it up.

[LT7A]

Ambitious project! You are making strong efforts to keep the upper hand on corrosion in the future. Good work. I have a question. You mentioned 3.21 gears. I wasn't sure which differential you are referring to. Was it a 10 12 or 14 bolt?

[Honest Bob]

Originally Posted by LT7A

Ambitious project! You are making strong efforts to keep the upper hand on corrosion in the future. Good work. I have a question. You mentioned 3.21 gears. I wasn't sure which differential you are referring to. Was it a 10 12 or 14 bolt?

Thanks! It was a matching 10 bolt and 14 bolt full floater. I sold them and went with 4:11's.

[Honest Bob]

Got the cab on and the hole cut in the cab for the removable hump I saved from the other truck.

oh yeah and it runs!

https://www.youtube.com/watch?v=Dklt1IxL1vM

[Greenlee]

Nice work! The new body looks solid.

[Honest Bob]

Originally Posted by Greenlee

Nice work! The new body looks solid.

Thanks! Yeah the body is really solid for a 75 around here.

[Honest Bob]

I had the throttle body gasket the wrong way around causing a vacuum leak so its running a bit better now. The Fi-Tech ecu is still learning it just needs some time I think.

https://www.youtube.com/watch?v=x5Ds6xh0Jjo

[wixthedog]

Looking great! You are doing solid work for what appears to be a fairly small shop, I know the feeling well!

[Honest Bob]

Originally Posted by wixthedog

Looking great! You are doing solid work for what appears to be a fairly small shop, I know the feeling well!

Thanks! Its a 20x20 this weekend I hope to get the 7' 11" truck out of the 8' garage door. I really could have used a bit more room during this project, but I cant move until the truck is back on the road.

[wixthedog]

Originally Posted by Honest Bob

Thanks! Its a 20x20 this weekend I hope to get the 7' 11" truck out of the 8' garage door. I really could have used a bit more room during this project, but I cant move until the truck is back on the road.

I ran into that problem before and ended up having to air down all of the tires to get it to fit! Good luck.

[Honest Bob]

Big progress but not alot of pictures since its been dark when I get home. Got the front end and bed on. The passenger fender to door alignment really spun me for a loop. Apparently I needed a spacer under the front passenger side of the cab mount (luckily found it laying on the old frame still!). Spent a good 12 hours on it.

Replaced the lap belts with three point belts from the other truck. Just had to drill a new hole in the floor.

[Honest Bob]

Rest of those pictures.

[LT7A]

On a serious note, you have done a great job of building a very capable truck. I hope you keep going with the level of detail that you have been attaining -- It's cool to watch!

[Honest Bob]

Originally Posted by LT7A

On a serious note, you have done a great job of building a very capable truck. I hope you keep going with the level of detail that you have been attaining -- It's cool to watch!

I swear my drain pan is highly magnetic, at least my tools arent going to rust! Its been over a year of work but I should be very close to being able to drive it reliably soon.

[Honest Bob]

A replacement proportioning valve fixed the brake fluid leak. Got new front and rear driveshafts made up. Also started getting the new hump and its matching part installed and applying sound deadener in the cab.

[Honest Bob]

I decided to make the 2nd panel that I cut out removable as well (rivnuts are awesome!) so next time the transfer case needs to come out I can remove the seat and use an engine hoist instead of wrestling that beast in from underneath. Oh and I added a cucv rifle mount.

[Honest Bob]

Completed some more sound deadening and filling in the hole for the manual trans in the hump. The white hump I bought on ebay I believe came from a blazer which turned out to be longer than the pickup? It all fit up so whatever.

[LT7A]

Good work - somehow I missed the last update. And tell us more about the cool new squarebody. Your new wheels and tires look the business. Just right for the rig, I think.

[Honest Bob]

Originally Posted by LT7A

Good work - somehow I missed the last update. And tell us more about the cool new squarebody. Your new wheels and tires look the business. Just right for the rig, I think.

Thanks!

The new truck is a pretty clean 1985 M1009 Blazer that just kind of came along. You have to have a back up squarebody for when one is down right? Right. I'll have to get a build thread going for that.

[LT7A]

Originally Posted by Honest Bob

Thanks!

The new truck is a pretty clean 1985 M1009 Blazer that just kind of came along. You have to have a back up squarebody for when one is down right? Right. I'll have to get a build thread going for that.

For sure a backup squarebody, haha! In my world, I call them parts trucks. And then when I get them home, I decide to build them instead. I'll look forward to the build thread.