Could a teenager build this in one month?

[Yukon Jack]

You mentioned there was no hole in the floor for the transfer case shifter. Is the tranny hump a part of the floor or bolted in. If the tranny hump is not bolted to the floor, that is not the cab that came with the truck. All 4x4's have the bolt in tranny hump. No big deal but that means the VIN on the cab will not match the vin on the frame which will cause you problems when you got to title the vehicle.

That is a very big undertaking.

A running motor from the junk yard maybe $200.

SM465 4 speed tranny and NP205 transfer case with adapter probably $250 to $300.

Front and rear driveshafts if new or rebuilt will run you at least $100 per shaft.

So many little things are missing or will need to be replaced. I'd venture to guess you will have more than $500 in little stuff, brakes, shifters, steering column, interior. like all rubber lines will need to be replaced. Will need new or good used tires too.

Do you have the funds for all of that? That and time are the deciding factor. Looks like a great project, but just be realistic about what it will take time and moneywise - AND GO FOR IT if you like a challenge!