I checked into it and was told that you can turn an AOW shotgun into an SBS on a Form 1. Personally I would just call Mark Serbu and tell him you want one registered as an SBS. I am sure he would do it why would he care it makes no difference to him how he registers it. Obviously he go's the aow route to avoid the $200 tax stamp. He might request you pay for the gun up front before he will register it as a SBS.

When Alan ordered mine he had to make it so it took a few months.