Thanks for all the help. I ended up filing the bracket slightly where the nuts and bolts attach, testing for continuity at each step. Once I put the bracket back on, I got continuity from the light bulb socket to the battery ground. After hooking all the wires back up my lights are working correctly!!! This is good, since I originally thought my problems were with the in-cab light switch.
Ok, so here is a question for those doing frame-off restorations. If you paint your tail light bracket and the tailgate where it attaches, won't you fail to get a good ground when you reassemble everything? Or from the factory, I wonder how the ground path was ensured given the painted parts?
