Can a 1996 Ford explorer engine be put into
a 1994 Ford explorer?
The two trucks engine compartments are almost identical. The body changed in "95, and Ford added the V8, which I owned, in "96. V6 to V6 should be virtually identical, so yes. A V8 into a "94 should fit, but everything around it - intake, exhaust, electrical, etc. - would differ and would make a much more difficult substitution.
Something to consider if both are 4.0 OHV engines. The 4.0 OHV engine went through six (I know of) modifications to the engine. A lot of the internal parts, and the heads were modified and not interchangeable. If you need engine repairs down the road, make sure to label the engine or tell the mechanic which model vehicle the engine came out of.