I want to keep the original motor tranny and rearend.
I'm not sure I was kidding. If you are not willing to change the motor, trans and rear you have very limited options to increase your speed.
Another helpful thought would be to always drive downhill.
The T-5 transmission was available in Jeep Cherokees, S-10 pickups and Camaros and Firebirds. And Mustangs and Astro vans.
How do you plan to use this truck? Some description of your plans and intended usage might better match the suggestions you get to how you'll use the truck.
