I have a 1992 GTR with the projector headlights, there is plastic pieces that the actual bulb get's pushed into. It has a spring loaded thing to lock it in place. I really only need one but a pair would be fine too. I had to modify them for my HIDs and I kinda FUBAR'd one up a bit, it works fine but the epoxy I had to use made the bulb un-replaceable so I would really like 1 more done the right way in case I have a bulb die on me...
it's the piece I circled in red, thanks- Don