Jason,

Check your PM.

I am hoping to find a local source but if not I found a few sources for native plum (Chickasaw) seedlings. I am not certain that Chickasaw is the best stock but I know it grows here so...Meanwhile, I will do a quick check on Dave's Garden to hopefully get a vector on these establishments.

Edward Fort Nurseries
Mossy Oak Nativ Nurseries
Oikos Tree Crops
Willis Orchard Co

Don't order from Willis.  I get all my rootstock from Raintree Nursery or Johnson Nursery and they never fail me.  Raintree has a great universal selection; Johnson has a great selection for the SE USA, and their people graft on-site, they also answer any and all questions with great recommendations, so ... if you're buying from them, they would be a great help if you can catch them when they're in the office-trailer.

    I have some wild plum bushes that I believe are Chickasaw with small red or yellow plums.The wild bushes are normally small ~ 3'-4.5' tall.

     Some of my domestic red plum trees look like the buds on this years wood will bloom in 5-7 days. I expect that the blooms or young fruit will get killed by a frost since it is way too early this year.

Another reliable source of rootstocks is Cummins Nursery.  Click on "Catalog" and then "Rootstocks" under the fruit you are interested in.  Nice people.   http://www.cumminsnursery.com/index.html

Out of curiousity ;), I grafted a Santa Rosa plum scion on a wild Chickasaw plum in February. It seems to be growing well.I will keep a watch on it in 2013 to see if it blooms at the same time of my other Santa Rosa plums.That is a wild Chickasaw behind the caged Santa Rosa grafted plum tree.