Free doesn't mean better. All the work you'll have to put into it for such little performance really isn't worth it. You can get a Chev 350 or Ford 302 (mustang 5.0, well..4.6 motor) for about $100 in a junkyard, and spend maybe $1,000 building it up and you'd have quite a powerful motor. Trans, if you're going balls to the wall, is going to be $1,000 max, and transfer case really varies. But the fun you'd have would more than make up for it.
I'm in the process of doing a Chev 350 conversion myself, and I'm using this site
as a guideline. Very helpful..you should seriously consider going V8.
is the website for Advance Adapters. The adapters for a 350 are child's play.