Look up both cars on Wikipedia. There's usually a fairly extensive list of all the transmissions used in various years and models. See if anything matches. That's not an iron clad guarantee because, 1) its Wikipedia, and 2) there could be electronic differences between model years on the same model of transmission, but at least that will give you somewhere to start.
Search Pontiac Grand Prix Questions
Pontiac Grand Prix Experts
Related Models For Sale
Used Cars for Sale