To find a suitable replacement for your 1994 Firebird V8, you'll need a transmission that's compatible with the V8 engine. You'll need to determine the specific transmission your Firebird originally had (e.g., 700R4, 4L60E) to find the correct replacement. A suitable replacement would be another automatic transmission designed for that specific V8 engine and year range.
When searching for a replacement, pay close attention to the transmission's year, model, and engine compatibility. A parts store or salvage yard specializing in GM vehicles will be a good resource to ensure you get the right fit. They will likely need your VIN number to verify the correct transmission.