73 K10: Blinker, Brake and Rev Light Issue - HELP!

[Burgersquatch]

On your bulb sockets, the single bottom point you mentioned.  Have you checked to see if that single point on the bottom side ( or back side ) is not corroded where the wire attaches to that single point ? 
     On my 74 if I remember correctly I had to fix a couple of these connection points and wires.

I haven't gotten to any socket wiring yet. And without the truck running and in reverse, I couldn't get any power to the reverse lights to test them.

[Jason S]

If you turn the ignition to the "ON" position (just before the start position) that would provide power to all the circuits without the engine running. Set the parking brake or chock the wheels and then move the transmission position selector to "R" to run your tests.