New, old member here. I'm in the middle of building the OHV into what most guys on this and other threads are considering...ported heads, cam, unshrouded valves, large dish 99 pistons for lower compression (in my heads) standard bore and stroke and an intercooled, turbo with a small amount of boost. Then there is the rebuilt transmission, the 8.8 Explorer axle with welding and a rebuild for peace of mind. (Not my first or last engine rebuild fyi - been doing this a long time)
I have spent a basketfull of money.
There is more to spend if you have an auto - most of them won't take boosted torque for long. The stick shift trans from Mazda that Ford used are not exactly Trimec's either. But, I'm not building a racer, I'm just making all the running gear in this truck new or improved. Still a boosted 4.0 has more than enough torque to bust things depending upon how you drive it.
I'm also shopping for another Explorer as a third car. It is amazing how many $600 soon-to-be hunting lease Explorers are out there with both 5.0 and 4.6 engines. For 2200-3000 in Texas you can find licensed and registered rust-free Explorers. (see any Texas Craigslist)
The wiring and 5.0 from an Explorer would convert my Ranger to a V8 for which race parts, 800-1000 horsepower (auto) transmissions are plentiful. If you are talking stick shift even more stuff bolts up to the 5.0 - most of it cheap plentiful and available at the wrecking yards.
I swear I have already spent more money on this truck than if I had bought a 5.0 Explorer, a pair of ported heads and a $350 shortblock, and put Mustang intake upgrades on the engine and bolted a C6 or something like that to it. If I remember right the 99 Mustang 5.0 could get close to 500hp with the right stuff - I'd settle for whatever
I'm going to finish the project as I started it. But think about the difference in price and availability of 4.0 rebuild parts vs. the 5.0's instant torque and hp. The V8 swap even it is more $ is dollars better spent if your are going for the big numbers - at least that's how it's looking to me from this end of the checkbook.