Not sure what your friend has done to make his run so great, but the 91 is the gen 2, which weighs depending on the style, 2800-3200 lbs stock. and the gen 3 is 3000-3300 stock. If your buddies was a reg cab, mostlikley it hardly weighs over 3000, mine stock was 3300, but when I had it on the scales a few months ago it was 4000+, which is quite a bit more than 3300. So the 4.56 are actually just about right, but many on here have told me to go even higher. Also, when I had only 30 inch tires a few shops said that 4.10's wouldn't be worth the time, and the 4.56 were perfect.