Ah, you are ensnared in the 85-to-86 tail light change mess. BTDT.

Basics: Lower outer lights changed into 2-filament bulbs and require three contact bulb holder and different circuit board.

Driver Side: Tail light unit can be used almost as-is, just needs a 1986+ circuit board. Installing that will require that two of the little points that fit into a hole in the circuit board - for location accuracy - must be cut off of the tail light unit. Cut them real flush. It will work OK. BTDT

Passenger side. Lower outer bulb holder must be white. (Black on the driver side.) The bulb holder key lug - the wider one - is in a different place than before, and the tail light unit has therefore wrongly keyed slots.

If you put the white bulb holder into a pre-1986 tail light unit, it won't end up with the contacts touching the right things on the circuit board, even if it's a 1986+ type board. There's a way to make it work. Requires making a "bridge" and putting a bit of insulating vinyl tape on the circuit board. Takes a picture to really explain it well.

Unfortunately I am not able to send a picture. Sorry.

Hope this helps anyway.

Good LUck,

Bob

:>)