[ no. 3 answer...........describe "spark plug wire" test. How was this test done exactly. What do you mean by spark plug wire? Where was the spark plug? What part of what wire? at plug, at distributor?????????? From what to what did the spark jump? How far did it jump?
The ol' screwdriver in the plug wire, (at the plug end, not cap), make it arc to metal on the engine.

@ No. 8 answer.............what is the yellow wire? What color is the resistance wire?
I can't find the exact wiring diagram for that truck, but I believe the yellow wire comes from the starter, and the resistor wire is clear insulation with a visible braided wire shielding below.

Have you installed the relay?
I don't have the relay yet

I know alternator has nothing to do with starting, I was making sure it was wired in right and belt was tight.
I won't disturb any wiring, and will have pics soon.
thank you

Jimmy Deveney
‘66 GMC 3/4 ton pick up
4 speed manual
305E V6