If you have a wiring schematic in a truck manual for that year it would also help. I rewired my stock 49 one wire at a time replacing as I went. I used the schematic in the book to confirm wire gauge.
As far as color goes I went against conventional wisdom by making mine all black in the engine compartment because there are only a few wires, headlights, generator, parking lights, horn and the longest run from the fuse box to the terminals is only a few feet. Easily traced if need be.
However wires under the dash and going back to the tail lights and gas tank sender I did use color. On the 49 the wiring is pretty simple.
