I believe the trace goes to the #2 plug in the connector from the
wiring harness.  If you can find another rear lite set the metal trace
can be removed by trimming off the tops of the tabs and lifting it up,
that will give you the bulb connections, put one in the hole of your
rear lights, line it up right and put the metal part back on.  If you
use a hot melt gun or silicone seal to hold the metal in place it should
work.  It should be a simple matter of running the wires from the stock
two position fog lite switch to the rear for the lights, you did pick up
one of those switches from those rabbits in the junk yard didn't you.
        All kidding aside I have another set of lights in my work drawer that I
intend to modify and install in my van,  I just haven't got around to it
yet, I hope this helps.

        DrRufo
        SOCal-81 vanagon