it depends on what you will do with the car... the allfordmustangs page that was posted above also has an optimal gear calculator for the 1/4 mi depending on your trap and unless you are trapping around 107+ it is pointless to have anything less that 4.10's (according to them) then u just have to decide whether the higher rpms are gonna bug you on the highway. and last but not least. the SOTP feel between the auto and stick is usually thought of as being one full step (i.e. 4.10 auto feels like 3.73 stick...) so a general rule of thumb is 4.10 auto, 3.73 stick, even though thats not optimal for the 1/4 mi. but maybe a streetcar...