I own a small number of pre 64’s. The feature I miss most in the pre 64 is the milled in feed lips. The designers of the pre 64 used a good feature found in military rifles from that era. That is the feed lips were milled into the sides of the receiver. Feed and extraction are critical features in military rifles and designers pay particular attention to features that ensure reliable function. Milled in feed lips don’t wear, don’t bend, and if properly machined, work forever. Today’s rifles depend on the lip contours of bent sheet metal magazines. While it works, I have had rifles where it did not work all that well. You can spend hours tweaking the upper edges of the magazine box trying to get a reliable feed.
This thread started before the new FN model 70 actions appeared on the market. I have a couple of the new FN actions. They are better built than any pre 64 I have handled. Pre 64’s show a lot of tool marks, and they were filed to fit. Parts don’t necessarily interchange, you have to fit them. This makes the assumption that your new part has enough material to file.
The new FN action has an improvement, that is the bolt shroud is now extended to cover the left receiver rail. While that will block gases going down the left, I have not seen anything blocking gases going down the firing pin shaft. Like every M70 built, wear your glasses because a pierced primer will vent right into your eye. I have come off the line with grease covering my shooting glasses from hot gases squirting down the firing pin shaft.
This FN action was one of the last to come out of New Haven, and it has the old style M70 trigger. That feature is now gone.
I prefer the claw extractor as I can open the action and roll a round into my hand. Actions with spring loaded ejectors will throw the case off the shooting bench. A properly designed claw will last forever.
I am unconvinced that a controlled round feed is “more” reliable in feed than a push feed. In fact, I think it is more difficult to get one to feed reliably. That extractor cut on the right side of the barrel will catch a bullet tip that wanders over there.