What is your end game with the car. What tire size. I'd first recommend going online, look at some of the speed, rpm, gear , tire calculations. And see what your choices may give you rpm wise and speed wise. I have a 98 convertible with auto. Engine only revs to 5200ish stock. So your rpm limit needs to be taken into consideration also . I would determine your rpm at your desired speed with O/D button off . Then consider gear choice