I have an upper that is 10 1/2 inches long.  What are my options as far as putting it together wtih a lower?

*Turn it into a pistol (and if so what type of receiver)?

*Can it be turned into a rifle of anykind (meaning with a butt stock)?

*If I get  a receiver that is registered as a pistol can you put a stock on it?

Also I'm trying to figure out who makes this upper.  The only markings that I can find on it are an "FK" on the side of the upper by the rear site.  On the front site located on the side of it is an A (then an R1 with a circle around it) followed by the number 1.  On the other side of the front sight is the letter F.  Would there be more information under the forearm like stamped to the barrel?

Sorry about all the ignorant questions, but thanks for your help.

You can put it on a lower (without a stock) if that lower is marked "pistol" or has been marked on the 4473 as such.

Do not, under any circumstances, mount a lower with a bbl length of less that 16 inches to a lower with a stock.
That is an SBR, which is taxed and regulated - if you make one without paying the tax, ATF will probably come and shoot your dog.
If you want to make an SBR, send a Form 1 off to the ATF.

Quoted: Do not, under any circumstances, mount a lower with a bbl length of less that 16 inches to a lower with a stock. That is an SBR, which is taxed and regulated - if you make one without paying the tax, ATF will probably come and shoot your dog. If you want to make an SBR, send a Form 1 off to the ATF.

If they shot my dog my wife would probably send them a bonus check. LOL.  Thanks for the clarification.  Any thoughts on what make my upper is?