There are 3 types of HUD's for the Cutlass Supreme
The Gen 1 HUD was used from 1989-1990 (and in the 1988 pace car replicas).
The GEN 1 HUD was larger than the GEN 2, had the height adjuster on the top of it, and the dimmer switch was located on the LEFT of the steering wheel.
This is a REALLY old pic of my 1988 (kinda embarassed to admit it). You can see the larger GEN 1 HUD on the dash, and if you look just above the headlight switch, and more towards the door, that is the dimmer switch. I don't have the HUD installed anymore, but I still have it, so if you need better pics, just let me know, and I can get you pics with them OUT of the car.

The GEN 2 HUD us what I have in my 1988 Cutlass Supreme now, and was used from 1991-1994. It is smaller, and has the cable adjustment. The dimmer switch/height adjuster is located next to the DIC just above the center console.

The shifter kinda blocks it, but you get the general idea. That is the stock parts for the Cutlass Supreme.

The GEN 3 HUD is what was used in the 1995-1996 Grand Prix, but so far, I think it will fit in the Cutlass Supreme. The Cutlass Supreme was SUPPOSE to get it, but I have only seen 1 with it (it was a 1995 Convertible). It uses the same dimmer switch as the Grand Prix. I am in the process of installing a 2000 Grand Prix HUD into my 1995 Cutlass Supreme. I am using a stock 1994-1996 Grand Prix dimmer switch for it (no pics yet).
If this is for a 1988-1994 Cutlass Supreme, I would HIGHLY recommend the GEN 2 HUD. It is smaller, the image is clearer, the dimmer/height switch is backlit, and it sits better to the dash (cover sits on dash, wheras the GEN 1 goes into the dash).
If you need pics of the hole in the dash, and shit, just let me know. Since the Cutlass is not my current daily driver, I can take it out to show you.
Also, the Gen 2 is easier to MOUNT. The GEN 1 is attached to the dash PAD, but the gen 2 is attached to the CARRIER.