You can get a custom serial numbered, heat treated receiver from NoDak Spud to match your trunnion.
You do not have to "demill" the old receiver.
B-West did not use a good grade of steel in their receivers, so heat treating it would not work.
If you are sending the rifle out to be repaired/rebuilt, the person doing it can return it directly to you. As you already own the firearm and will be supplying the replacement receiver, which you already own and have done the paperwork on.
Price quote:
Disassemble, inspect, clean parts from current rifle: $30
Reassemble parts with new receiver: $60
Refinish using Brownells Gunkote to include bead blasting: $60
Test Fire, final cleaning and lube: $25
Shipping to be determined.
I assume you will supply the rivets, a magazine, any compliance parts and the new receiver.
Old receiver will be returned to you for your disposition, Rifle, magazine and any unused parts returned.
I am a FFL and have built many AKs and RPKs and have all the tooling required.
Contact me if you are interested.
If you use a different FFL, he should:
Send you a signed copy of his FFL
You will need to verify the FFL using the BATFE website
Ship the firearm to the address ON THE FFL and no where else.