I believe it was around July 2000 the '01 trucks started showing up with rear disks. The 2001 trucks built during Jan - June 2000 had drums. It was at this time we began to notice many things were being deleted. . . trucks with drums were missing fender liners, hood liners, lighted vanity mirrors, tailgate applique, no more painted intercoolers, etc. A lucky few had the disks AND the items most were missing, but these trucks were rare.
Vaughn