I would never rely on a manufactured stock made by a duplication company to fit your gun. Unless there was plenty of wiggle room built into the duplication. Hand fitted guns such as Parkers have so much variation, that a one size fits all approach does not work. It is a different story if you are talking about a Stevens 311 or savage 99.

The absolute best thing is to duplicate from your original stock so that there are no surprises. When I duplicate a stock, I usually leave the outside profile about 1/8" oversized and the Inletting about 1/32" undersized so that it can be finished by hand.