upper assemblies and any other parts OTHER than the AR Lower receiver can be shipped to your door.
Only attach it to a Lower that was purchased as "OTHER" or "Pistol" in a Pistol configuration unless you have done the stamps for SBR and are compliant with the 29" Overall Length (stock extended) MD rule/law/whatever
If the 10.5 is the barrel and you have a LONG muzzle brake, you can pin and weld it too to make it total 16"
Not a lawyer but be careful about constructive possession if you don't have a pistol or registered SBR to put it on first but do have a rifle that can mate with it. But otherwise you are good to go ordering parts online other than serialized piece.