ive been in stangs and rode with quite a few gear ratios.
been in a stock 2.73 gears in both AOD and t5 cars. USELESS, not near enough gear and need to pulled out and thrown in a crucible to be melted down to make some higher ratio gears.
been in a bolt on 5.0 stang with 3.55s and a t5, car ran great and felt awesome.
been in mild 5.0 with 3.73s ran great.
i have my car with 3.90s, mine also has a 2.95 gearset trans
been a near stock t5 car with 4.10s ran ok.
IMO if your just going a bolt on or HCI on a 302 or something and dont plan on too much power. i would suggest 3.55s- 3.73s.
IMO its easy to overgear a stock or near stock 5.0. i've been and seen many 5.0s get toasted by cars simply for the fact the low gears put them out of their powerband too fast.
i mentioned the near stock t5 car with 4.10s. IMO the car didnt feel all that fast, it just felt low geared. i dont know about most guys, but to me there is a difference in a TRUE power SOTP gain and the SOTP gain gears give you. the 4.10s in that car just didnt seem to be the best match IMO. now if you had a car with better breathing heads and cam that operates at higher RPM where you can take the car to 6000rpm instead of 5000.
3.73s seem to work pretty good in the cars i have been in with them.
my 3.90s seem to work alright, when i was oringally N/A they worked alright, when i put my SC on and made more power. i hated the lower gears. the car with more power would blow tires off and with the lower gears it would blast through its powerband way too fast. i feel a set of 3.55s would have been a better match for what i had.
now that i have taken the SC off and sold it. the 3.90s seem to work a bit better. but still feel a little to low geared.i'm going to have my turbo setup going here soon hopefully and will be swapping to 3.27s, to load the car more and help the turbo spool in lower gears.
i also rode in a near stock car with a t5 and 3.55s, this car has just bolt ons simple stuff. stock heads and etc. probably a 14 sec car. to me this car ran really good.
granted the car had a really good driver. but the 3.55s just seemed to keep the stock engine in its powerband on the street. had plenty of oomph from the 3.55s but didnt have the "running out of steam" feel that really low gears give you on a stock engine in 3rd and 4th gear. overall the car didnt feel slow at all and it ran great on the street.
so here is MY rule of thumb.
stock car or HCI N/A car, or stock engine SCed car - 3.73s seems to be the best, or 3.55s work great too.
supercharged HCI car making alot of power across the board - 3.55s or so, with that much power you dont need lower gears..
turbo car - 3.27s possibly higher geared if making LOTS of power
if going for a pure drag deal. its best to dial in the gear ratio to cross the finish line at your max HP rpm in your 1:1 gear (or non OD)