Real difference once again is basically upper intake, and fuel injectors. The long block is the same on both engines with the exception for a 2 wheel drive versus an 4 wheel drive vehicle. Regular Explorer 4wd and Sport Trac 4wd, plus 2wd are compatible for engine swap just requiring the long block to be the same (4.0 SOHC). Koda is correct.
Long block is an automotive term for an engine sub-assembly that consists of the assembled block, crankshaft, cylinder head, camshaft (usually), and valve train. A long block does not include fuel system, electrical, intake, and exhaust components, as well as other components. The yards are just referring to what's listed in their guide and this swap has been done here many times.
I brought a 2007 Mustang 4.0 2wd drive entire engine to replace my 4.0 2003 4wd engine. We used only the long block from the Mustang and changed the upper intake, fuel injector, fuel rails,spark plugs and wires, engine wiring harness and other upper intake parts from the Explorer Sport engine.