I agree with Mike, the TransGo shiftkit is the way to go. It really wakes up the truck, but listen to Mike about the settings. If you do decide to get it though, follow instructions to the "T", have plenty of patience, and a clean floor. While I was working on mine one of the few springs you have to take out flew across the garage. After a few choice words, ranting and raving, I found it. Some other kit to consider is the Baumann Engineering kit(hope I spelled that right), I haven't heard too much about this one though.
98 Nascar Edition
Homepage
http://www.freeyellow.com/members8/jackhel/index.html (I have some serious updating to do to my site.)
Powerdyne Supercharger, Superchip, Autometer Boost Gauge and Pod, K&N Filter,
TransGo Performance Shift Kit, Flowmaster 40 series Muffler, Taylor 8mm wires And
Bosch Plantinum Spark Plugs, Gutted MAF, 4.10 Rear End Gears, XTRA Bright Halogen
Lights, Amsoil Series 2000 Synthetic 0w-30 Motor Oil, 2 inch rear lowering shackles,
G-Tech Pro Series II, Bedliner, 100w driving lights, Aftermarket stereo stuff, Cobra
75WXST CB Radio, Wilson Antenna, and some other stuff I can’t remember.