A boosted 4.0 OHV is a torque monster. There have been a few over on RPS through the years. They're not common, so parts and knowledge can be hard to come by, and expensive when you do find them.
The cheap "Explorer 5.0" swap that people do isn't all it's cracked up to be. It's easy to find them, and typically cheap, but they're not great engines out of the box. They made 215hp at the crank when they were brand new. It's more than other Ranger engines, but it's pretty terrible power for an engine that size. They can make some power, but you have to spend some money to get there, on top of whatever it costs you to do the swap.