Except with the parking lights switched off and the red wires pulled at the tail lights - the harness side is dead and the terminal on the light socket is hot.
I'll probably do some more hunting and pecking around when I can think of something non-destructive. I may try the SuperbrightLEDs in the auxiliary sockets since they do behave differently than the Pilot bulbs.
8 Feb - tried the Superbright LED in the auxilliary sockets and they behave as before - wouldn't flash when parking lights are turned on. I'm also getting voltage bleeding through the bulb from the flaser circuit to the park light circuit although the park lights are off and disconnected at the tail lights. I checked for voltage at the fuse and it was 0. I can even duplicate this by hooking them up to a battery charger. But - they work fine in my GTX. So, I'm pretty much done for now. No Mas!