Define "blown up"
And no on swapping in a 4.0l OHV, it can be done but isn't a good swap.
1993 Ranger computer is EEC-IV OBD1, 1995 and up Fords need EEC-V computers with OBD2.
Also uses different fuel systems.
And Explorer probably has an Automatic trans so you need a computer that matches that trans model to control it, and a 4.0l OHV EEC-V computer(1995-2000) probably wouldn't have the Control software needed.
Yes, it gets complicated now a days.
I would look at renting an engine lift they are not that much for daily rental.
2-ton with long arm, measure from center of the engine to front of the bumper, needs to be at least that long.
Buy an engine stand, 1,000lbs stand runs $60-$70 new, or look for used, you can rent these but you never know how long it takes to get parts or to do the repairs, things come up, so buy one.
Good read on how to pull the engine here: 1 SOHC V6 Engine Removal Procedure - Ford Explorer and Ranger Forums "Serious Explorations"®
Even if you find another engine you still need to pull the old one out and put the new one in.
And you are right, buying a used engine(or vehicle) is a gamble, you could be buying someone else's headache.
The timing chain issue on these engines was fixed with a new design of the parts, so a timing chain kit will come with the new designed parts, and once install they will last.
Blown head gaskets are wrench work, nothing fancy involve, both heads should go to machine shop to get checked and new valve seals installed(new valve seals come in Head gasket kit).
Don't feel comfortable doing this engine rebuild work?
Call a machine shop, ask them how much to rebuild the "top end", and install the timing chains, if YOU drop off the engine to them, and then pick it up when complete.
Don't buy the engine stand, remove engine from vehicle, strip it down as much as possible while on the hoist, load it into pickup, and deliver it to the shop(they will have their own lift to remove it).
Most of the labor cost in an engine rebuild is removing and replacing the engine in the vehicle(10 to 16 hours), and it is just tedious wrench work that can be done by semi-skilled labor.
A good skilled mechanic has to charge for his knowledge and skill whether he is using it or not, he has earned that right, so he can't charge $25/hour because he doesn't have to think, lol, his rate is he's rate, brain on or off.
If you hired a Botany Professor to mow your lawn it wouldn't be $10 or $20 like the kid down the street charges, lol, but job gets done the same, whether you pay $10 or $1,000
No need for you to pay the higher hourly rates if you can do it yourself or get someone else that is "learning" to do it, for a lesser hourly rate.
There are options
And even partially rebuilding your current engine is a better bet than "buying someone else's headache"
See if you can find a local "DIY mechanic" that can help you out, he will have the tools needed and may like the extra CASH, ask around.
If you don't have a Place to do it you can rent garages for a month just for this type of thing, look in local places, craigslist, buy and sell, ???..........