if you go with a 5 speed, check out the Tremec, the TKO is the heavy duty model.
i still saving my pennies, but here's a gear ratio comparison:
Tremec 5 speed - 1st 3.27, 2nd 1.98, 3rd 1.34, 4th 1.00, 5th .68
my T10 4 speed - 1st 2.64, 2nd 1.75, 3rd 1.34, 4th 1.00
with this comparison, it looks like i could keep my 3:07's and get better take off (read buy new rear tires or smokem' if ya got em'), 2nd gear would be close, but a little stronger, 3rd and 4th exactly the same and then be able to shift into 5th and cruse 70 mph @ 2000rpm (it's 3000 rpm now). with the 3.27 1st gear and the .68 od you sort of get the best of both worlds, although i have heard people say that the split is too big between 1st and 2nd. with this trans you could run your 3.70's and it would act like a 4.58 in first and a 2.52 in od when compared to the 4 speed. i think you can still use your console with some shifter mod. if you go with the auto, I'd try a 400 unit with maybe the new overdrive/underdrive units that would give you 6 gears. don't know too much about them, but lately the hot rod mags have had a few articles. check the archives on this board for more research.
To see a pic of my car, click here... pages.prodigy.net/mtbmtb/rf396ss.jpg