Hey, mac, I just had the same situation in August on our 1963 1/2 ton. All stock. Had cheap after market fuel pump fail, and after repairing it, ... No lights, ignition, etc. Seemingly unrelated to the fuel pump fix. Like you, I had voltage from the alternator.
I eventually discovered the wiring goes through the firewall through multi- prong plugs,
and I had to pull these and clean the contacts. Then I had normal juice!
Hope this helps, good luck! I know I was pulling out my hair( not much left)
