Some things to think about. For best launch you would think a 4.56 rear gear would come out of the hole better than a 3.73 rear gear. Yes it does but if you have a low stall torque converter (2000 RPM) with the 4.56 rear gear you may not get out of the hole as fast as a 3.73 with a 4000 RPM converter. Speaking of a vehicle that gets traction, not one that spins the tires. When I dealt with lighter cars for the strip the Powerglide was choice. 1.76 First gear in most of them and we would stick in a 5.14-5.46 gear but with a 32-33" tall tire. How about a 3.89 gear with a 2 speed Glide and a shorter tire. Would you run a 4000 stall to get a good launch. I would or maybe a bit more stall speed. The reason I bring this up is a little math 1.76 first gear in the Glide X 3.89 rear gear. You get a 6.84 first gear ratio. Lets look what happens with a 3 speed TH 350 with a 2.52 first gear. 2.71-2.73 rear gear puts you right in the 6.84 first gear ratio. Yes a Highway gear and the TH 350 is darn near the same as the Glide with a 3.89 gear. You would not go drag racing with a 2.73 rear gear and launch very well. Or could you???????? Lets say you used a 4,500 with that 2.75 rear gear and the TH 350..What happens now? When I was setting up my 57 for a drag race against my friends 550 Wheel HP mustang i pulled the 3.73 gears and stuck in some 4.56 gears. The launch on the street during testing still felt weak. I pulled the 2500 stall and stuck in a 4500 Stall Coan converter. Now it felt right I got a great launch with it. If you make enough TQ I think you could do well with a 2.75 and high stall with the TH350 I may be testing that theory soon. Fun with numbers.