1. The rule on using a receiver to build either a rifle or a pistol appllies only to new receivers from the factory that have NEVER had a barrel or stock installed. No one is going to buy the idea that a M-N receiver is newly made and was never a rifle.
2. Cutting up a rifle receiver into several pieces, just so it can be "remade" into a pistol might (or might not) be legal, but to me it sounds like trouble looking for a place to happen when the gun (whatever it is) is fired.
3. PTK, I assume that pistol is registered as an SBR. If not, ????