for a NOS harness..I would agree that's a great deal even if you have to mod it some.

I would try to cut pieces out of the old harness to lengthen wires as needed to keep it color coded. I like to solder connections then heat shrink them up good.

have you done the amp gauge bypass? that's the big problem on those yrs. heater circuit as well, it likes to melt the fusebox.

if not at least have a look at the wires/back of gauge cluster to look for burnt/melted plastic.

good luck.