Do these kits have to ship to a FFL?
NO. Under ATF law's you can build ANY weapon of your choice so long as you are Legal to own one in the first place and it is legal in the State where you live.
Because the "receiver" in this case is being built by you ( its considered an 80% receiver) no FFL is required. However, you can NEVER sell it. Unless you get the required Manufacturers Lic, put a Ser# on it and go thru an FFL for the transfer. Something like that anyway. Its been awhile since I had to think about it.
So find everything you want and have it shipped straight to your door