Cardude, no need to pay all kinds of transfers and fees, you will be registering the existing serial # on the Form 1, then after approval, install that 7,10, 11 or 14 inch barrel you choose to use.
As far as he "MAKER MARKINGS",,DO NOT FOLLOW
"CIB's" advice. The only thing you have to do, and it DOES NOT have to be in plain sight,,,,remove pistol grip,,,and engrave your
first initial,, last name,,city,,state on the large flat that pistol grip slips onto, re-install pistol grip,,,all done. If you have a C2 register, then you will have multiple transfers and cash handed out, can get up to $400 and some pay-ola for a C3 to hand the transfer if he decides to ask for handling it for you, DO IT yourself and use that $$ to buy your short upper. If you need help, call me, as I have (2) approved Form 1's. HAL