Need a purchase advice for Pontiac!!!!

Hi leudls!!! I really rides the purchase of a pontiac Trans-am, Firebird!! So I fulfill my little childhood dream (K.I.T.T.) 1-What should I look for??? 2- What is the difference between a trans on and Firebird?? 3-What about replacement parts?? I want to buy the 3 liters, no more and then upgrade to car gas!! Does anyone have any tips??? Thanks already in advance lg Tobi!!