Never heard of soutac. I do own a 18" JRA that runs fine and a 13" SAR SBR built by hillbilly.
The 13", if its built correctly, its a lot funner range toy. Can you not just get them to build it as a pistol and then if it runs good, you SBR it? Galils are pretty easy to swap in a stock or brace.
In my case, hillbilly has a great reputation. I ordered a kit and a receiver, SBR'd the receiver, and sent it all to him to put together. There wasn't really the gamble you're taking if you go with the small noname shop.
I dont know if i would take the gamble with the noname shop if all they offer is the SBR/NFA. You wouldn't even get to take the gun home and shoot it for 9 months. It could be a dud the entire time you're waiting for the stamp.
There was 1 dude on the akfiles who got a SAR build from southern tactical. If thats soutac, then we have at least 1 data point. His gun had canted parts pretty bad. It got sent back immediately.