Aaron, Buds does not accommodate custom serial numbers unfortunately. There are several places that offer what you need : -- bravo21tactical.com/?page_id=13 ------------ yorkarms.com/receiver.html ------------- allstartactical.com/services/custom-shop

York arms offers custom serial numbers yorkarms.com/receiver.html
So does trail blazer firearms trailblazerfirearms.com/product/ar-15-receiver/

Aaron, BUDs may not be the place for that. Don't think they will do custom serial number lower. Would be better served contacting a company like PSA. Bear Creek Arsenal or many other companies that could make you a custom serial number lower.