Steve, Only two were the actual pace cars (one was a backup). They both had "sunroofs", so celebs could stand and wave to the crowds. I think they are both still at Conner Ave., the original in a Customer/Greeting room, and the backup on the plant floor. The backup may have been moved to the museum, but I'm not sure. Here is a pic of the original (taken in 1998) in the greeting room:
Sorry for the poor res, but I had a POS camera back then.
As you suspected, all the rest (but not all '96 GTS's) came with a decal set.