Jack, yes the bolt holes on the chevy/pontiac clamps do not match up. As far as I know, the stock buick ones are a bit deeper. I also forgot to mention that I am currently running a 34mm because I got some dough for a 36 that I couldnt turn down. Just by looking at the picture, I am going to make an assumption. IT looks like you have the chevy brackets there and the 36mm bar bushings. Well if all that goes together, then I would take a guess that the bushing probably sits up in there a bit on the chevy. (unlike being flush on the buicks) Go get a buick bracket, 4-10mm bolts is all the brackets are to remove. Just go in and out of a U-pull-it self serve auto parts, and snatch yourself some brackets. I got mine off a base regal. Not too back breaking in my opinion. Not to mention, you dont wanna be drilling any more holes in your car until its swiss cheese. Just get those brackets and go from there and see where you end up. Let me know what you find.
Scott