I have '89-93 mustang 5.0 HO in my 4dr which ways 6000+ lbs. The engine does not produce enough torque in my opinion. Oh ya, I have 33" tires 4:10 gear and a stout AOD trans. I'm also at 5820ft above sea level. I too like keeping the "mustang" belt driveline for future crazy mods.
Keep in mind newer "mustangs" use the shorty waterpump so the aftermarket will make and does already make screw superchargers for this belt line.
The stock HO heads and intake do not produce enough torque to move the explorer. I believe you have a sport...this may be less of an issue for you? If I did it again I'd put a 347 stroked 302 with good heads and GT 40 intake. All that take some $s. For less $s use a 1996 Explorer with GT40 intake and heads. I don't care for the "P" heads because it limits header choices.
There is plenty more info out there...search...