Gear ratio?

If you're doing 4 grand at 60, figureing a little converter slippage, I'm guessing that you've got 4.55 or 56 gears. If you're doing mostly highway driving and have 14" tires then I'd highly recommend 3.23 gears. You could purchase a center section (pumpkin) with 3.23 gears allready installed and set up then drop the drive shaft, pull back the drive axles and simply change out the center section. A used center with used but good gears shouldn't cost more that 700 bucks. Ask around. A new set of gears and to pay the time to someone to set everything up on your existing center will cost nearly that much.

Terry