Probably, the easiest swap would be a year model-for-year model, V8 Explorer to Ranger. Find yourself a '94 (or newer) 'sploder with a 5.0L that some insurance company is considering as totalled (or someone is ready to part with), with an intact engine/tranny and do a direct swap. Repair/Overhaul as needed. Take the computer, wiring harness, fuel system, the whole 9-yards. Might even take some of the exhaust, although, it won't be as conducive to HorsePower as headers and a custom exhaust. Don't part with the donor until you are sure you've stripped everything from it you might need or want.
I would suggest that you forget "conversion kits". Kits will sucker you with 1 or 2 item(s) that you really need and others that won't work for you, and you will have wasted your money. Search the forum(s) and do your homework. Buy individual parts as you need them. With a little ingenuity, some stuff can be fabbed by a crafty backyard engineer (i.e. engine mounts). I always ask myself, "Will it look like it belongs?," and "Is it safe?"