Montero will work for a straight bolt in, but you may have to swap over your accesories and intake and injectors. An 89 has different ecu and dizzy, but is otherwise fine, and a 91 should be a direct fit. Others may chime in with other almost fits...

Mopar minivan 3.0's use a different oil filter mounting (under the motor mount in a rwd application, instead of front pside).

Welcome aboard, we have several MM/d50 folks on here...

Not responsible for advice not taken...