Parts Transferability... Half Ton to 1-Ton

[CowboyProtectionUnit]

OK I realize that the Main Parts Springs, Front Differential Inards, and axles and Such aren't transferable... but What if any Parts are... Here's What I'm doing... Taking this...... my 87-88 GMC 2wd Crew Cab Dually and Converting it to a 4wd.... Its Been Suggested that I find an buy a Donor Truck... and I'm curious if I need to be looking for a 1-ton 4x4 or since I'm planning on rebuilding the front differential I can get away with a half ton or 34 ton 4x4 since I tend to be finding More of them just lying around here lol

Thanks again Ya'll