.........First, I am not sure I have ever seen an engine that is not "over head valve"................
My '55 Willy's had a Flat head 6 "Super Hurricane" engine, no OHV.
You are just too young
Yes the 4.0l OHV to 4.0l SOH"C" swap would be a complicated swap because the 4.0l SOHC was introduced when Ranger was an inclusive wiring nightmare, got the GEM and also have to deal with PATS anti-theft.
That is the reason you don't see alot of these swaps, other swaps are more practical and can have more power.
If you were swapping a 4.0l SOHC into a 2001+ Ranger with 2.3l or 3.0l then maybe not so bad, but into a B2..............lots and lots of work with little reward at the end.
You would be better off looking at V8 swaps if it is the power you want, been done alot so few surprises.
Oh, and two-strokes have no valves
But the piston "acts" as the valve letting exhaust out and new air/fuel in, so maybe it could be consider a one valve engine, admittedly a stretch, lol.