Since you have both vehicles, and I assume both are parked, I would take the doors off and try the Explorer door on the Sport Trac. I asked the same question a couple of years ago when I came across a perfect Explorer door in the salvage yard already off the Ex, and we never came to a definitive answer. We looked at collision part #s which seemed to show different parts, but a closer look showed the # for one of the vehicles was for the door, and the # for the other was for just the outer skin. The parts diagram and lists didn't show both parts for either the Explorer or the Sport Trac. Looking at my son's Mountaineer vs my STs, I think the front doors interchange, but I'm in the minority. The top of the door glass opening is the same because the same window visors fit both. I've seen an '01 2dr Sport with an earlier front end on it,(or vice versa), and aside from the body line over the wheelwell not blending into the door trim, the door fit perfectly. Obviously the (removable) trim panels are different, and that alone would be why interchange manuals for used parts are going to show different parts. We're not going to know for sure until someone tries it.
