You can send your lower to
Orion Arms to have it engraved. They do a fantastic job. Turnaround time is about a week. Also, you only need to have your name, city and state engraved on a SBR. You can buy short uppers just about anywhere that sells complete uppers. Check out
CMMG, I have had good luck with them. If you end up buying a barrel and need it threaded, I can give you the info of the guy who does mine. You will probably never need to show your stamp when buying shorty parts because of the proliferation of AR pistols. That and it is not the manufacturers' problem what you do with a <16" barrel.