If you change transmissions you could go with many open driveline OD transmissions. To give you an idea, a standard 27% OD will make your 4.56 gears feel like 3.34 gears
Possible transmission swaps include but are not limited to the T5, A833, and NV4500. I would not reccomend a T5 in a truck larger than 1/2 ton, but then again it all depends how you will use your truck. If you still have the 216, you might have to swap out to a 235 or 261 to give you more power.
