v8 swap in a 55 1st series

[enick72]

I'm new to the forum and have been looking into a few different trucks to buy. I used the search feature last night but didn't have much luck but that may be due to my phrasing.
I am looking for information about how much work is it to swap the 6 cyl. or transmission or both in a 55 1st series truck while keeping it mostly stock. I found many swaps with front clip replacements but for now I'm more interested in just a swap of partial drivetrain. The truck I'm looking at has been in a barn since 1977 and there is no key so the seller is not sure if it will run. If it does run I dont mind the 6 cyl at all but may want to replace the tranmission for better driving conditions.
Any help is appretiated.