At my job I replaced the ohc engine with an ohv one. Very simple all I needed was the ECM, engine harness, ignition switch assembly, and the controller behind the glove box. Can't remember the exact year of them, but I had a wrecked one for everything so I didn't need to mess with programming the PATS system, which the donor had. Everything just plugged in and ran perfectly. In my personal Explorer I had a 4.0 OHC and blew it, then I bought a 5.0 drivetrain and set my body on it. The engine harness plugged right into the chasis harness and it all worked great! If I remember correctly, all I had to do there was change the cluster control box, if thats what its called, with the 5.0 one because of the flashing 4X4 lights having AWD instead of 4WD.