the 4.25 is most likley the back spaceing which would put the offset at -25 or -32 I'm guessing. They should work fine if your going with a 4" lift kit, but they will stick out a little bit and you may want to get some fender flairs to keep the mud off the side of your truck.
The 315's fit my truck with 2" lift in the front, but with the factory wheels the tires rub the springs. Factory wheels have a +10 offset for trucks up to 04, and +40 (tire sits farther in) for 05 and newer trucks. The perfect set up is to run a 16X9 wheel with a -5 offset(for early trucks), but...