I replaced my backup light sockets with dual element sockets from a
trailer light kit. Harbor Freight has one that looks like it onsale:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41782 .
The sockets in the kit have a strap across the base with two holes
that match the nut plates on the stock backup lights. I salvaged
the stock nut plates; and used them with the new sockets. The results look
like the car came that way!
The trailer light kit also provided a wire harness that easily
reaches the dash with molded QD plugs similar to what Stude used. I made
a "break out" harness from my light switch, and turn signal switch, to the
molded plug from the trailer kit that normally attaches to the tow car.
This is especially easy if you have a tilt wheel. My new lights plug in
under the dash; and have their own wires all the way to the switches. There
are no splices; since I soldered new buttons on the wires at the sockets.
Lenses from "Nostalgic" match the stock tail lights if you line
inside the trunk lid with chrome tape or foil around the lights.
I also grounded all four tail light sockets to the frame bolts in
the rear corners of the trunk. I think that the stock grounds are the main
cause of dim tail lights in Avanti's.
The results were lights so bright that I decided I didn't want high
power bulbs. The increased lens area to the rear is a valuable
improvement.
I haven't bothered to install backup lights on the end of the
license plate, yet.
Mike M.