If you're talking about a body lift kit, it is basically a set of spacers that fits on top of the body mounts&bushings with longer bolts. For safety reasons, you should make sure the mounting brackets for your body bushings are not rusted or wallowed out. You may need to have new mounts welded in if that is the case. Any brand of kit will work, but the most popular is Performance Accessories.
If you need help or guidance on the body mounts or bushings, just ask. I replaced all of mine with polyurethane bushings from Daystar instead of the rubber ones, and it was a real chore. I purchased a complete kit from Rocky Mountain Suspension. This is normally the best time to install a body lift, but I just replaced the worn out bushings.
I bought new bushing assemblies for the two front ones under the radiator from LMC Truck. These even had Ford Motor CO. on the box. The Ford dealerships discontinued such items for pre-90 Broncos/F-150's years ago.
I will tell you that I am not a big fan of body lifts, and feel like a suspension lift is the way to go to increase ground clearance and fit oversize tires.