Welcome to the group!
Just when you think you heard it all... The Poly Tech National Match was imported into the land of shall not be infringed in 100% ATF approved condition. Unless the seller lives in a state that requires strange things to be done to the rifle, there was no reason to have to modify it. The National Match was imported with a semi-auto only receiver, so I have no idea what would be "needed".
Also, they were imported before the Bush the First ban on evil looking features, so it is exempt from the 10 parts rule of the new ATF second amendment known as 922(r)
Now if you did find stuff in the receiver that doesn't look right, could you take a few photos as well as one showing the whole receiver from either side. Looking for an illegal 3rd axis pin which would mean it was built using a true AK receiver (full auto at one time) which should not have been allowed into the land of shall not be infringed.
All above assuming you are in the USA since we are a world wide forum.