Thought yall could shed some light on the wire harness

[RoughKuntry]

So owning a 73 4x4 project truck I have been looking for ways to go around the main problem of the harness. So when I swapped out the cabs on my rig I noticed that the previous owner did some things wrong. Not saying that he did a bad thing but crossing a 84 truck harness with a Cadillac. I am of need of a stock Harness Chevy/GMC. But I did get to thinking what about rebuilding the harness? Has anyone else thought about doing this instead of buying a painless harness at $650.99. I'll update when I can.