I recently installed two 55 watt add on back-up lights (actually
rectangular utility lights), on my '85 Westy, and what an easy job it
was.  Drilled no holes, cut no original wires, and used a standard Bosch
type relay.

In the black box on the forward firewall is a connector for the back-up
lights (yellow plastic covering spade connectors).  One side has a
single blu/blk wire that comes from the back-up light switch and the
other side has two blu/blk wires that go to the factory lights.

I separated the connector and made a wire with two female ends so I
could connect the wire from the back-up switch to pin 85 on the relay.
I then made a wire with one female spade and ring connector on the other
end which I ran from relay pin 86 to ground using the grounding bolt
below the coil.  That caused the relay to "Make" when the van is shifted
to reverse with the ignition on.

I then made a wire with a female spade on one end and a ring connector
on the other to run from relay pin 87 to the standoff inside the black
box where there is a constant 12 volts.  That's the standoff where the
wire(s) from the alternator go.  That's what will power all back-up lights.

Next was making a wire with one female spade and at the other end a male
spade with an additional wire (two wires crimped into the male spade) to
run from relay pin 30 to the connector for the original back-up lights
with the 2nd wire from the male spade running back to the wires for the
new back-up lights.

Now, shifting to reverse with the ignition on "makes" the relay and
routes power from the constant 12 volt standoff to all back-up lights.

The relay I added fits inside the black box and is protected from the
elements.  All you see is where I ran wires out of the black box through
the grommets at the bottom.  Shrink tubing was used on all spades.

BTW, my new lights are secured to my tow hitch bar with hose clamps
running through their brackets.  Now I can SEE when backing up at night!

Mike