See Figures 1, 2, 3 and 4
There are two basic automatic transmissions. The first is the two-speed Powerglide which was available until mid-1973. The second type is the three-speed Turbo Hydra-Matic, which is available in four load capacities, Turbo Hydra-Matic 200, 250, 350, and 400.
The four types of pan gaskets used on the automatic transmissions used in the Firebird are pictured for ready identification.