If I'm shopping for a lower of any type, I look at the firearms sections of any website. Not the parts section. As anyone can order parts, but it must go through an FFL to order a lower. So I've been conditioned, for lack of a better term to shop for lowers this way. A complete lower with a rifle stock I'd look in the rifle section. A complete pistol lower would be in the pistol section. A stripped lower would be listed in the AR section of both.
Bingo!