electrical frustration

It's a 74 duster and yes I have the wiring diagram. I know how the dome light works on a grounded switch circuit. The drivers door works fine (after replacing it) and the passenger door passed a visual inspection. I never checked it for corrosion/good ground, so I will be sure to do that next time I get over to my garage.

I will also check the grounding and make sure the gauges are not on the same circuit as the lights as well. They work fine until I turn the lights on, so there is some funky interaction going on there.

As for the dash lights, they did work fine after I hooked them up and I really think the problem there is with the short I know about and haven't had a chance to work on yet at the fuse block. It is definitely not the rheostat or corrosion on the switch as it is a brand new Ron Francis switch I just installed. Good info though, you have given me a few ideas to follow up on...thanks!