long block only?
If you decide to use a Mustang (2005 thru 2010) SOHC V6 you will only be able to use the long block. Everything else (wiring harness, intake manifolds, all accessories, etc.) must be swapped over from your 1998 Explorer to the Mustang engine. In addition, the Mustang has different fuel injector seals and no crankcase breather. Due to wiring harness changes, sensor changes, fuel changes and intake manifold changes the only "plug & play" engine swap is a 1997 or 1998 Explorer or Mountaineer engine. If you are willing to use just the long block then you can use any Ford SOHC V6 from any Explorer, Mountaineer, Ranger, Mustang or even a Range Rover Discovery III. Several members have gone with the Mustang engine and there is a good thread documenting the swap. All of the camshaft timing change improvements are incorporated in the 2002 and later engines. Some members think the Mustang engines have additional camshaft timing improvements but I doubt it.