I have a 1991 firebird, the car was side swiped and the fender, door and side mirror is messed up. I am doing the body work, but I can't figure out how to get the mirror off to replace it. there is a piece that comes in front of the bolts I need to get to. the camaro I took it off of at the junk yard did not have the annoying piece.

 

I took mine apart back in 2002 but I dont remember this can you post some pictures so we can look at

 

the piece is in the top right corner, blocking the bolts I need to get to to remove the mirror.

 

Been there, done that. I assume you refer to the black 'rubber triangle' between the door window and the windshield pillar. You have to remove that. If you look carefully, it is attached to a bracket. There are bolts up top, and another one at the lower end of the bracket, with a big fender washer under it. It is a PITA to twist and wiggle that thing out, but you have to do that in order to get at the bolts for the side mirror.