I finally spent some time with Baby today. I swapped the side marker units just for grins and the left unit worked fine on the right side. This verifies the SM sub harness, receptacle and lamps are operational. The harness male receptacles are the same on both ds and ps.
I was able to get voltage on the turn signal wire but not the parking lamp wire. I was tracing back the harness and found these two wires had been chaffed on the engine frame. I cleaned, soldered and sealed the wires and everything checks OK.