I have a 2004 4X2 Sport Trac with a bad engine. In my area used 4X4 engines are available but 4X2 engines are not. What must be changed on a 4X4 engine to put it in a 4X2 Sport Trac?

 

You know, this is a really good question. The answer is that I have no idea. I've worked on a ton of these, and right off, nothing is comming to me about any major diferences.
As far as I know, with the exception of accessory mounting, these engines are pretty nearly identical. There could be something different in the 4X4 mounting, but I doubt it. Most of that bolts to the frame. One big difference could be the oil pan (the front diff. might get in the way), but the blocks are the same. One other question might be the engine mounts, but I couldn't see that, either.
You might research this a bit further, but the best thing to do is study the engines and see what could possibly be a problem.