Ford 4.0 OHV Engines

I've read somewhere that newer Ford 4.0 OHV Engines are interchangable with earlier engines. I have a 93 Ford Explorer Sport 4x4 with a 4.0 OHV Engine. I've read that basically these earlier engine are pretty much junk. I would like to put a newer 1997 engine in it. I've read that the only difference in these two engines are the intake manifold, wire harness and coil pack. Can anyone let me know if this is accurate?