Just to clarify: The 455 came out in 1970. It became available in the Firebird/Trans am in 71.
It depends on what you plan to do with your car. Show, cruise, daily or occasional driver, drag or street race. I plan to go to shows and cruises with mine once restored. I plan to put a lot of miles on it, but keep it in very good condition for a long time. With this in mind: I am keeping it as original as possible, but some minor updates. Also keeping the Sprint 6/4spd combo for good HANDLING and overall performance. Good gas mileage also........ Basically decide what you will do with it, and enjoy it!!!!