Not sure if this will help but I recently put a Stevens 200 4.4" action with centerfeed into a an earlier Savage 12FV 4.25" stock that was originally a stagger feed. I moved the front action screw hole .139" forward and notched the rear screw area for the tab on the centerfeed mag. I made a shim about.310 to fill in the space in front of the magazine and used 1/4" rubber shims to take up the slack on the sides of the magazine. It fits nice and snug in the stock and rounds feed smoothly into the chamber.