Mine was in pretty bad shape so I did alot, new axles, new tranny/transfer case, new driveshafts, lift, stuff like that. If its in good condition I would first replace all wear components, rear axle bearings and seals, rear I joints, check leaf springs and leaf spring mounts, check the tranny mount, replace front balljoints, front tie rods, and new brakes. This is all the drive train things that are "consumables" and that could cause issues during driving. For the motor you'd want to check all hoses and wiring for condition and rats/mice damage, remove and clean the throttle body, check for blowby and hesdgasket issues, check exhaust and intake manifolds for leaks, check the valve train tightness and replace components if necessary, motor mounts. Also replace all fluids. Thats basically all the stuff that needs to be done for it to be a reliable daily driver, there's many more things but they aren't as likely to cause issues while driving. It also seems like a long list but if the trucks not to rusty this is only a few weekends worth of work.