1995 Oldsmobile 88 thread and accurate measurements on brak

I will try to help you.
but I don't understand what you are asking for.

cant you take measurement from your tail light housings?

I tried to take measurements but the threads dont match. I have tried just about every bolt size I can get at hardware stores. I have been told from various mechanics that is a propietary bolt that is made only for certain cars. I called a dealership and to no avail they wont give me any info so I can duplicate it. I need a parts supplier or parts info. I tried asking this question once before but even though the answerer was really helpful I needed to do more research. I have been to salvage yards and still no luck.

I do not see any screws that hold the brake lights on to the body of the car.
There should be 3 studs attached to the tail light housings and then nuts are threaded onto the studs to hold them on the car.

the nuts are 6x1mm thread.

This is great information. So just to make sure I understand cause when I look at my other light there are those "studs" that are threaded. These go through the housing and into the frame with nuts on the end. So realistically speaking I just need to use the thread size and find the proper length bolt. I am thinking these studs are made for Oldsmobile cars.

the studs are built into the tail light housing. and Oldmobile will not be able to sell replacements to you.

You will have to rig something up on your own, or get another tail light.

I often put side view mirrors back on with studs that I buy at a hardware store and glue them in the housing with JB-Weld.

Good luck