i had a buddy who upgraded to disks in the back..he said he wished he had just kept the money, because there was no difference in braking. You have less maintenance with disks, but he said there was little to no change in braking. i would get some performance front and rear brakes. thats my .02
I agree with FYI101. You can get a set of Powerslot rotors and Hawk performance brake pads for the front from 4wheelparts.com for about $200. That's exactly what I did along with new drums and shoes in the rear and I couldn't believe it was the same truck.