Ok everyone - thanks for all of the advice! I removed the reverse light bulbs, disconnected the PNP wiring harness and tested pin 5 (to reverse lights) to ground - no reading (OL) - no continuity - so no short in the wires between the PNP and rear lights. That left the PNP itself. Got one from FCP -...

Thanks again Neil! You were right on the money. Axle support bearing. I didn't wind up replacing the bearing - I ordered a remanufactured A1 Cardone axle and put it on. It might not have been the cheapest way to go, but having never worked with the axles before it was a good learning experience. And...

Thanks again for this info! Used 7219 bulbs from replacementlightbulbs.com - they were $2.90 for 10 bulbs. They're the same as the Radio Shack 272-1092 - but since most of us don't have access to a local Radio Shack anymore I thought I'd share! Cheers to MVS.