Did you really think mult-meters were given to the techs, what for to trouble shooting? Yes the wiring can be real can of worms on old vehicle with cracks on outer wire cover, just image where you cannot see, That's why you are replacing all wiring period will save headache in the furture, for you Ron.
You know, what's funny, is the manual actually details repairing AC compressors, starters, and carburetors. I'm glad I'm inspecting every circuit on this truck. Not in a hurry, as I shared with a friend who visited yesterday. I'm going to buy some 3/8" loom Monday so my new wiring, like this B/U light circuit. When done, I can see some more work. For example, I observed only one of the three side marker lights work.
My red LED instrument lights came in Saturday, so I took a peak at the blue bulbs in the instrument panel to see if I can get them out without destroying them. Looks like I may have to take the circuit board off to get them out. I'll study on this before taking any action and while I add the wiring for my new tach and vacuum gauges. The circuit board could be more delicate being 41 years old.
Another observation while deep into the electrical wiring is how perfect the body, paint and details. Seat, dash, new carpet, new window and door rubber, and the bed looks like no one ever used this as a pickup truck. The wheels are the original factory ones, but like so many I've seen, likely had significant rust on the chrome. The builders look like they sanded and powder coated them silver and put chromed trim rings, which looks really good. Much later on, I can figure out if I want them chromed or not.
After all the electrical is finished, hopefully next week, I'm going to pull the wheels and inspect brakes, lines and calipers. There's a mom and pop transmission service I'll get the transmission inspected and serviced.
So, still lots ahead before getting her on the road.
Cheers, Ron