[84LX89GT]

Well the transmission won't bolt up, you'd need to convert it to an automatic, but both stangs and explorers have A4LD's as autos so you should be able to make that work with a swap, or get an adapter for the T5, or find a M50D from a manual ranger or explorer and convert it. You'll probably have to do some rewiring, probably not all that major but still they have different wiring harnesses. You will have to use the processor out of the explorer. You'll also want to get a 2 core or larger radiator from a mustang. There will be about 100 small things you'll have to bend or fabricate as well as i don't know
if the oil pan from the 4.0L will clear the crossmember of the mustang. It'll be a different swap, but it'll probably be more money than it's worth, especially for an engine that is notorious for having cracked heads (4.0L OHV). Good luck, that's all that i can think of.