uh oh, you got me thinking on that. went and dug out the old light assembly and compared it to the new one (that "genuine vw" bus depot item). there's a bit of difference. pics:
old piece terminals, from left to right: BL, 31, 54, 58, RF
new piece terminals, from left to right: BL, 31, 54 (top), 58 (bottom), RF
please bear in mind that i've got a 78 westy, could be some wiring differences for other years, etc (i just don't know). the difference is: in the original unit (top of pic, looks 30+yr old) plug 58 has two posts (lt and rt) and plug 54 is set opposite 58, the replacement (bottom of pic, shiny and new) plug 58 has one post and plug 54 is right next to it. dug out my notes from when i was removing the lights.
driver side light unit was set up this way (letters, numbers stamped into the plate, and both new and original units have them, excepting the lt and rt notation i made to differentiate the split post 58- it shouldn't matter tho):
BL- black wire w/ white stripe
31- brown wire (GROUND)
54- black wire w/ red stripe
58, lt- white wire w/ black stripe
58, rt- solid black wire (which goes to the left side marker light)
RF- solid black wire
passenger side light unit:
BL- back wire w/ green stripe
31- brown wire (GROUND)
54- black wire w/ red stripe (2 identical wires use 1 push-on connector, one continues over to the driver side taillight)
58, lt- white wire w/red stripe (2 identical wires use 1 push-on connector)
58, rt- solid black wire (which goes to the right side marker light).
this shouldn't be a major problem, just put a splitter on the one fat terminal ( new light's 58) to accomodate 2 thin ones. problem solved! (i hope)
it dawns on me now that i might have misinterpreted the wire color, won't know till i can go check (it also dawns on me that i just locked my garage key in the garage, will have to wait til tomorrow to gain entry). it is possible (likely, in fact) that one of the white wire w/ red stripe from the pass side housing (58, lt) goes over to the driver side housing (58, lt). i thought it was white wire w/ black stripe, could be wrong on that one. that's gonna bug me til i know for sure... crap...