Old, rusty bulb sockets are the pits to deal with. You might have to do some surgery on the tail light assemblies and adapt new, clean sockets to the housings, with dedicated ground wires running from the new sockets all the way from them to clean, tight connections on the frame. Ditto for the license plate light.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!