[Ron61]

Not exactly sure I understand your question, but your engine's torque is going to stay at whatever RPM it is now. But the lower gears will get you to that range quicker and it will feel a lot stronger from a stop. Tire height will also play into the factor. With 25" diameter tires and 3:27 gears, I am taching 2525 RPM at 60 in 4th but just 1900 RPM at 70 in 5th as it kicks my ratio up to 2:10s. That is in the Cobra which is lighter than your brother's Mustang. I have a .6 split and if you went to a .8 that would lower the 5th gear top ratio. I think Joe is right on about the gears as the Mustang weighs more than the Cobra.

Ron