Replacement engine companies??

Has anyone had experience with the replacement engine companies out there?? I was looking at ATK. I'm looking to drop a new engine into my XJ but dont just want to grab one from a junk yard. I think I'm going to just go 4.0 to keep it stock reliable, and hopefully have better MPG's. The only problem is I believe these engine companies are going to provide me with a 0331 head.

You could look local. I have found that the circle track racers know whos the best engine builder, follow them.

just find one from someone parting out an xj. I got the engine thats in my xj with 60k miles for free and the one in my garage for a case of beer with 90k miles (we had to pull it though)