Have a 1950 Chevy 3100 and a Classic Parts wiring harness.
Wiring diagram for 1950 and harness instructions mostly match but not with ignition.

Harness has a small accessory harness with a blue wire that goes from coil (+) to ignition switch. The large red wire is supposed to go from starter motor switch to ammeter. That seems pretty straight forward.

Harness instructions show a large red wire going from "B" terminal of voltage regulator to ammeter (-). The wiring diagram, however, shows this wire going from the VR B terminal to ignition switch (with ammeter and headlight switch wires joining along the way). I'm wondering if I could just use this harness red wire to go from voltage regulator "B" terminal to ignition as shown in the diagram and then use a short wire to jump from ignition to ammeter (-).

The wiring diagram shows four "wires" joining in a tiny white circle near the ammeter. It shows a long wire going from B terminal on VR to ignition switch and then "short" wires going from ammeter to this circle junction along the route of longer wire and another joining the headlight switch.

The remainder seems pretty straightforward.

I'm trying to find the "You are here" arrow and the piece of cheese at the end when you solve the maze.