well here is the deal....it *might* be possible
the HUD is a 8 wire hookup....if you have the FSM from your donor car and a FSM for your car then it would be alot easier
my biggest concern is that the vaules that the HUD sees is the same as the pervious gen...
here is somethings you need to consider...
you wont have the HUD windshield...possible double imaging
you will need to mount the HUD switch somewhere
you will need to mount the HUD
you will need to cut the dash
you will need to fabricate a trim panel for the HUD
now the 92-95 have a cable driven adjustment for heigth...the 96+ have a electronic adjustement
it would be a big project, but bigger things have been done on the early 90'* SSE'*