I have been in your shoes, 'cept my parking lights were on the fritz.
Seems the halogen reverse bulbs were pulling too much current and fried
the headlight switch and the switch on the tranny. I replaced the
headlight switch to get parking lights and planned to do the reverse
switch, but I no longer have the car.
As I recall, odd as it may be, the power for the backup lights first went
through the headlight switch.
86 4kCSQ gone and missed
96 A4Q nearing the 1000 mile mark