The ground is in good shape. I actually tapped into that ground for both my driving lights, and the tachometer.

I think I found the problem last night. I pulled the rheostat plug back out, and put a test light on it...and flipped the switch. Nothing. Hmmmm.. Peeled the tape off, and checked out my soldering job again. Put the test light on the bare wire, flipped the switch......and BINGO, the test light lit up! When I was messing around with it the other day, I somehow pulled about 90% of the wire away from the plug, so it wasn't making any contact. I couldn't see this, but it was broken underneath the wire sheathing. The break is way too close to the plug to solder back together properly, so basically, to do this right......i'm prolly gonna have to snip a another rheostat plug off a salvage yard unit and leave myself with a few extra inches of wire.

I'm not 100% sure this is gonna solve my problem until everything is hooked up again.....but i'm guessing this was the gremlin.

Thanks for the help guys!