I am using an alternator now so the voltage regulator is gone. In its place is a key-on fuse box using modern type fuses (since if you are out east of nowhere you won't find the old style fuses). It is roughly the same size as the old voltage regulator and allows you to fuse-protect 12 items. There is another smaller modern fuse box for constant power items. Yes, many ways to skin the cat. I would have one fuse box for key on and one for constant power. And if you have things like radiator fan, please remember to use solenoids. Also HEI. A solenoid is helpful there. Especially if you have the original ignition switch. Part of this answer probably should ask "how much do you expect to drive your pickup?"
Around 1976 I created a new wiring harness for a 1951 GMC using the wiring diagram and the old harness (for lengths, etc). In that one the harness was pretty well shot from age and weather. It wasn't difficult...took me a couple of evenings and worked great...but as I said I've done this work before. And in 1976 you could find all colors of wire in all gauges. But I found it handy to use small pieces of masking tape to identify things like which side of the fuel gauge, etc. There really isn't that much to worry about on these, you know. Sort of like a VW beetle. You can rewire one of those in an afternoon (aside from the courtesy light wire). Good luck. If I was going to recreate a harness today, I think I'd do the work a section at a time. And I'd remove the speedometer. Makes it a lot easier to reach in there rather than to twist around and under. Good luck.
