The price of a new harness is piece of mind your truck does not burn down from 50 years of wear and tear and improper repairs done over the decades
crimp splices , wires twisted and tapped together are not as good as heat shrink and a clean solder joint for connections
Lack of clean grounding is most likely part of your issues others have mentioned it before me
Brothers and other places have Nos style harness kits buy the pieces you need today and buy other parts as needed
the fit factory harness like the originals did
https://www.brotherstrucks.com/69-72...tinfo/WH22075/