Lucky you! I believe wild muscadine vines can be male or female so not all of them produce fruit. I found a few articles from searching on google.com telling how to prune older vines that might help you. I don't have any experience with them myself. I have been researching whether I can grow them in southwest Missouri.

Gardenweb has a forum for gardening in the Ozarks that you might like since you're in Arkansas.
http://forums.gardenweb.com/forums/ozarks/

Here is a link that might be useful: Google search - Pruning neglected muscadine