I am wanting to build an AR and I am wanting a custom reciever with my markings.

Assuming I have my permissions from ATF "form 1 sitting on desk"

Can I have a machine shop cut out my reciever for me? Or do they also need to be a firearms manufacture?

If firearms manufacture needed can I get one to make it without having them stamped as manufacture or would they need to be stamped as manufacture above the tigger left side?

If i get an 80% reciever it be sent out for engraving to a non-firearm manufacture prior to its completion.
Should this be stamped engraved prior to polishing or after-yet before finishing