Not too many wires under hood. But not sure which you are exactly referring to. Should not be hard to duplicate one at a time and pretty cheap. You don't need different colors when you can visually follow a wire from A to B (unless all wrapped up in electrical tape). The colors are for tracing and to be GM correct. 2 or 3 wires needing replaced does not require a harness. All old wiring, not looking too safe....does.
As said, depends on your level of refresh/restore. Depends on the total wire condition. There are work/farm unrestored trucks that just need fresh wire to be safe and run good; and there are factory correct harnesses that do the same function.
A nice harness is a good way to go if budget is not too much a factor. I am trying to answer your question mindful of you saying you don't want a harness, just wires. Either way is doable.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
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