Ok, here is what you do.
Screw the 2.9 starter.
Buy one for a 1991 Explorer with AUTOMATIC transmission. That is key, a manual trans starter won't fit.
Then get a long double ended battery cable.
Install the Explorer starter (it will have a solenoid, don't worry about it). Move your current starter wire to the other big post of the fender solenoid and hook it to the little terminal on the new starter.
Then take the new battery cable you bought, put it in the location of the original starter wire and run it to the large post on the new starter.
Bingo, you just upgraded to a stronger, lighter starter. Took you 20 minutes.