Talk to these guys in Raleigh, NC.  I have never dealt with them but they sure have a great web site:
Transporter Werks - Raleigh NC

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| Transporter Werks - Raleigh NCYour VW and Porsche Restoration Specialist in Raleigh NC |
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I was going to suggest the Autobahn Society guys in Braselton, GA (northeast of Atlanta), but when I checked their web link it didn't work.  They might be out of business.
They were a conversion/restoration shop, and while they might not have done trannies, surely they would know of someone in the SE who would.
Perhaps someone on the list knows what happened to them, or if they are still in business.
Ant  (in NE FL)

      From: John Rodgers <jrodgers113@GMAIL.COM>
 To: vanagon@GERRY.VANAGON.COM 
 Sent: Wednesday, March 9, 2016 9:15 AM
 Subject: Tranny rebuild
   
Haven't so far found a single vanagon tranny rebuilder in the Southeast.
It's really hard to believe. There used to be two in Alabama near here but
one quit doing it, and the other died. What a bummer!

John