I don't think I'd want to plan to complete this swap in just one weekend. I've done swaps that fast, but never one with the number of changes and modifications I think you face.

What are you going to do to connect the shift linkage?

What are you going to do to connect the throttle linkage?

The wiring and fuel line aren't difficult to figure out on the fly, because wire and rubber hose are real flexible.

Check out what you need to do to adapt the cooling system. Will hoses that fit your radiator also fit the motor?

I would not want to have a drive shaft made until I could measure things in place.

These are just the first issues that come to my mind that you did not mention.

You ask about removing the rear crossmember. I don't recall if the 3800 has a transmission crossmember or not. If it does you probably want to remove that. If you are referring to the bellhousing crossmember be aware that it also adds strength to the spring mounts. I've seen guys trim that one rather than remove it.

I'd call Langdons and ask them to email directions. I'm surprised they didn't send you any.

I have a bare frame from a 1950 3800 sitting in my yard and might be able to take pictures of that if it would help you in planning this project.

I hope this helps.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...