Bring a USGI magazine with you and make sure it would drop free from the magwell, if it does then you are good to go. Fulton Armory has been making AR products for a while, I think they are a trustworthy outfit.
I bought three stripped Fulton lowers on a group buy a few years ago and mine were GTG. They seemed as good as most and better than some. Went together well and work fine.