8548 is not a stock replacement gasket. Most auto stores have them in the computer as a "stock replacement" just like the 9333 pt-1. This is because of the .50 compressed thickness. They both have the same thickness, and are the same gasket, except the 8548 has a different type of metal fire ring.
Go read some threads on the corral in the supercharger section, you will get alot of reading on these two gaskets.