I'm pretty sure the thumbhole stock is still considered a pistol grip by the ATF, so that isn't an option. You could get a Romanian SAR-2 or WASR-2 and get a romanian threaded FSB: http://www.k-var.com/shop/product.php?productid=16353&cat=290&page=1 . The ATF ruled that it is legal to use with a pistol grip since that thread size is 22mm, as opposed to the Bulgarian 24mm, and no known flash hider is available in 22mm. http://www.cs.cmu.edu/afs/cs/user/wbardwel/public/nfalist/atf_letter89.txt
The law says you can't have a threaded barrel that can accomodate a flashider, so as long as there aren't any flash hiders available for the thread size, threaded barrels are legal, unless "one should become available". The only thing you would have to do is file off one side of the bayo lug or another ATF approved method for permanantly disabling the bayo lug. The thing is though, they stopped imported Romanian 22mm compenators and the only source currently is a US made one from: http://www.ak-103.com/parts.html which is about $75 but will help with the US parts count. ...Or you could just permanantly attach the Bulgy compensator and disable the bayo lug using ATF approved methods. You can't use a Romy FSB on a Bulgy AK because of different barrel diamaters. Hope this helps.