Having Trouble Transplanting Stock Innards of Pistol Grip Stock to Field Stock - Benelli M4

[m4prime]

Hey all. So I ended up getting a free Benelli M4 field stock from a neighbor. It is obviously of some vintage or... just something different, as the plastic is obviously totally different. The buttpad says Benelli Spa Armi, which is kinda cool. 

Anyways, on closer inspection and trying to install it on my shotgun, I quickly realized it didn't have the internal hardware to thread the stock on. 

I then took my pistol grip stock and tried removing the innards to transplant them over, and ran into an issue getting the main metal plate as well as what appears to be many washers to slide off of the screw in there. I tried pushing from both sides with a long tool to see if I could wiggle it a bit, to no avail. 

Before ooga booga'ing it, I wanted to consult the forums first. 

 

Current State of the OEM pistol grip stock. Locking nut removed, and now I'm stuck. 

 

New (to me) field stock innards:

 

Thank you for the help in advance! 

 

 

[NCswamp13]

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