Ok thanks for all the input. I will use that calculator and consider tire size too. I'll let you all now what I will go with.

 

hehe...low hp and tq for Richard means less than 500 of each

 

Ok, so I got bored again and plugged some info into that Richmond calculator and here's what I got:

With the Ford Racing Cobra R T5 (with a 2.87:1 1st and 0.82:1 5th) and a 26" tall tire and 3.73's, I'd be turning just shy of 3k rpm at 75mph. Seeing as I'm running at about 3300rpm @ 70mph right now with my crappy 3sp manual, 24" tires, and 3.25's out back, I'd call this a pretty good deal. Two more gears to play with and slightly better cruising ability. I think I found my tranny/rear combo

 

ok, what would you need to do (5th and or diff ratio) to be doing say 2400 at 75.

my eventual dream is to make sure my car is not running at between 2050 and 2200 in 5th asexhaust tends to drone in that range.

 

The standard T5 0.68:1 OD gear puts you at 2460rpm @ 75mph with 3.73's and a 26" tire. That's a drop from about 3600rpm in 4th at that same speed.

 

Those ratios are what I'm looking for. That is a good setup, for me anyways. Nice job on the research.