Only the 03 and up have the six speed right? go 4:10!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! And top speed, mines limited to 154 mph I think, Do you do that often? Just do the 4:10's so you don't kick yourself later wishing you would have. Good luck
4.30's!!!! Dont do 3.73s. Top speed isnt affected since you accelerate in fifth with 4.30s. I have had mine up to 135 in fifth and it was still climbing good. Just keep searching and reading on all the boards you can like svtperformance, here, corral, mustangworld.
I love my 3.73, think its about as high as you wanna go if your worried about stop and go daily driving. Still gives good pull at high speed. Plus with your IRS if you go with 4.10 you definitely want to put in heavy springs, bushings and a brace while they have IRS out. Even with 3.73 you really notice wheel hop.
Also gettiing a set of Russel stainless break lines at same time, they have rear lines that would be easier to snake through IRS while its out of car. Just stuff to think about. Either gear set you will feel.