On 255/50-16 BFG Drag Radials I was crossing the line in the 1/4 mile at 120mph, pretty much topping 4th gear out around 6500 rpm. I liked the 3.91s in that car but if you plan on making over 400 rwhp I would suggest keeping the 3.73s. Turbo Supras like a longer gear to load the motor/turbo up, we don't have foxbody Mustangs with 5.0's where the "cool" thing to do is have a 4.11 posi track rear end haha. (no offense yota8791, i like mustangs too)
That CT26 was upgraded in January of 2005. I ran it for 20k miles running 20psi DAILY then sold it to my friend who has been running it on stock boost ever since. People can hate on upgraded CT's all they want, maybe I had a freak of nature or something but I loved that turbo, never had any problems out of it.