Can anyone tell me if a Winchester post-64 production "classic" action, with claw extractor will fit a pre-64 stock inlet? How much work would it be to get it to fit? Thanks.

No, the Classic action is slightly LONGER than the P-64, about an 1/8" of an inch and while you CAN adapt "layup" synthetic stocks as I have had two done, you have to completely re-inlet an wood blank, not often possible.

The extra length of the post-64 is in the magazine box. You have to lengthen the front of the magazine mortise and extend the inletting for the front of the receiver and the floor plate. You will have a gap behind the recoil lug to fill. No big deal if you glass bed. The screw hole will also move forward but piller bedding will take care of that.

The post-64 trigger guard is also slightly wider so the inletting has to be widened there.

They aren't the same distance between the screws are they?

Per Dick Davis, here are the spacings of the front to rear actions screws, center to center:

Post-64 long action = 7.575"
Post-64 short action= 7.035"
Pre-64 action = 7.450"