What about this T56
http://www.g-forcetransmissions.com/tran_gt-56.asp
Rated at 900 horsepower and 800 ft-Ib of torque, almost straight cut gears, changeable triple cone syncos, and you dont have to change your rear end ratio for race days. What I like is the 0.86 fifth and 0.75 sixth options, this makes a close ratio, for my app with higher revving Nascar type engine a 4.10 final drive ratio is in order which gives me 180mph at 7000, and 2300rpm at the speed limit!
Rockland Standard Gear make several versions
for the Corvette, Mustang/kit cars and Viper, the Viper trans has about the best shifter position compared to the original TL, the rest are to far back.