[skooter]

Robert,
"IF" the Firebird has the same pitman arm as the Camaro, which most should, the late 80s. early 90s S10 box works. It allows you to even use you stock power steering pitman arm. You need the one with 4 bolts on the cover, as in the pic. The earlier 3 bolt one will work also, but you need a different pitman arm as the boxes shaft is smaller. I think this also applies to the other applications, as well, earlier F bodys, Novas, Chevelles, etc.
The 4 bolt one is a little heavier than the 3 bolt, but should bolt right in. Mine came out of an 88 S10, 4 cyl., 5 spd, that's what they seemed to have come in. These are a popular item, they go fast in the junkyards, they do turn up on Ebay often.