Those leafsprings should just bolt on, the 95.5-97 have different leaf spring mounts, but the 98-04 have the same mounts. As long as those are made for stock mounting they'll work. You'll need shorter shackles, probably stock length since he got 6-6.5" of lift from the springs. You might sit slightly lower with the extra weight from the double cab so 1" lift shackles might work to depending on the stance you're looking for. You will also need new U-bolts for the install and I would get new front eyelet bolts (the bolt that goes through the front of the leafsprings and the frame) in case you have to cut the stock ones out.