Yeah, all winter I was like, gee I like to find a 3.21 rear end to replace my 3.91 rear--it works great and don't want to mess around with it. Yet first time I drove the car around here the 3.91 gear feels just right. The way home from the storage place in Detroit I still went 80 + mph...its got decent mufflers on both pipes-I run 2 high flow mufflers on each pipe to hush it down.
On paper 3.91's seem too much but my real world driving the 340 really likes it. Now gas mileage, lol