There is a lot of unneeded hate for the Post-64 Model 70 actions that comes from it being a "pretender to the throne" that the original M70 was. On it's own, the Push-feed M70 is a good action. It has the good design elements of the M70 receiver, safety, and trigger, and extractor setup. If it came out again today as an action under a different name, it would be quite all right.
I have one of the newer FN SPR's, and a Pre-64 hunting rifle. The only difference I can notice between the two is that the trigger on the SPR is made from a casting, wheras the M70 trigger is not. I am sure there are other things too, but seeing how well the current FN actions do, I am not too concerned.
From an ameatur gunsmith perspective, rebarreling the Pushfeed 64 actions is as easy as they come. Cut some threads, cut the chamber, and then chamfer the breech, and you're good to go. Pre 64s require an extractor cut. 700's require a recess cut into the breach for the bolt face.