As I said in the previous post, there are 4 brackets attaching the compressor to the engine. Here are pictures and drawings detailing them.

I think the long thin bracket just below the V bracket was only used for the 69 year. It is a brace from the lower rear of the compressor to the cylinder head. I'm not sure that 67s and 68s had that bracket.

These brackets can be found on eBay from time to time. They are listed now. Or another listing.

Another seller, MotorCityMuscleCar on eBay sells bolt and spacer kits to mount the brackets. This is a link to the complete kit.

There is also a guy ThePartGuy that has many Pontiac / Firebird A/C parts. He sells from the website and on eBay. His stock varies so you will need to check back from time to time.

Pete