AA 19.5" and 24" Barreled Uppers

[Bwild97]

Were any of you who own a rifle, that uses one of these Uppers; able to find an adjustable gas block that fits? .907 OD land, seems to be and odd ball size, as the only available sizes are .650, .750, .875, and .936. What is the OD of the barrel at the muzzle end, before the thread diameter? One more question, what thread does your barrel have? 9/16-24tpi or 3/4-28tpi

Sorry for all the Q's but I'm still weighing my options, and the AA barrels seem to have awkward dimensions according to the parts available on the net.