Interesting, that Raybestoes PG-D667AM rear pad set is listed for all 03-05 Sport Tracs, and also all 2001 Explorers built in 2001, not counting the Sport model(2dr's). Does that mean the late 01's had rear calipers with phenolic pistons?
Your rear brake pads should be no problem, if the calipers are not dragging. Any pad should last for many years on the back if the calipers work properly. The front pads are very important, they do about 75% of the braking work. So concentrate on the quality of the front pads. Those need to be very good, the lesser pads will wear faster, and are prone to make more noise.