What are you using the truck for? For just everyday use and towing, get a standard shift kit from TransGo or B&M. They're all about the same. If you're really abusing it, like racing or hard 4-wheeling, go with a B&M Stage 2 racing kit. It's a lot firmer (usually chirps tires in every gear

) but it holds up to a lot more.
If you want the trans to last flush the fluid, change the filter, adjust the bands, and blow out the cooling lines EVERY 20,000 miles. It would also help to put a deep aluminum pan on the transmission, and replace the stock cooler in front of the radiator with a large aftermarket one.