On my 1971 Cuda when the parking lamps or head lamps are on, the left blinker dash indicator light and fender mounted light (A01 package) turn on and stay on but are definitely not as bright as usual. They stay frozen on if I activate the turn signal. The right blinker lights work normally with the parking/head lights on, and all blinkers/lights work normally with the parking/head lights off.

Does this sound like a ground/wiring issue or a component issue?

start with the grounds for your parking light assemblies.

Ground issues do that. Usually when there's a loose ground or connection broke.
I've had anything from lights on very dim all the time to tail lights that wig wag.

As mentioned, its a ground problem. I had a similar problem on my Dart, the ground from the radiator support to the parking light housing was loose.

I agree on the ground checking, but possibly save yourself a little aggravation, check the bulbs front and rear, I have had the filament break and fall onto the opposite filament tower (?) and back feed the circuit.

I'm pretty sure I am not drunk and mis-remembering this ... but I am getting older ...

Thanks for all the replies. It was two issues. First I cleaned up all the signal housing threads/connector terminals/fasteners and got the blinker to work. However, my left fender mounted blinker would slightly illuminate if I put the parking or head lamps on. It went away when I unplugged the left front turn signal harness. I installed a new harness from PG Classic and it’s functioning properly. Now onto the next gremlin...

About 95% of these type issues are ground errors. Glad you figured it out.

great to hear you got it fixed !