The receiver must be handled by an FFL OR if you can find a non FFL who will let you wait while they do it (that way there isn’t a transfer of ‘ownership’). All other gun parts can go anywhere since they are the actual gun.
Well the actual process takes a few hours for something that size but finishers usually then have more time for processing the paperwork and packaging. We use a place in Alexandria for some of our fabricated parts. I can ask him if he does this or not and if so I will post it or pm the two individuals above.
there is a shop in rosedale md that do work for lwrc and adcor not sure they will do ones and twos might not be cost effective.eastern plating is the name