...and the generic TH400 filler tube available from the aftermarket suppliers will NOT fit your Firebird. As Vikki mentioned, its got some unusual bends in it. Again, I could not install mine...from above or below. You could use one of those flexable braided filler tubes but, you'll have to attach the top end to the firewall.

My engine and tranny are out right now. Let me know if you need a photo of the filler tube...