Will a pre war M70 bbl fit a post war action? Thanks, Bob

Yes.

The barrel shanks of all pre-64, as well as current production "Classic" actions, are nominally the same. Threads are 1"-16TPI; shank length is about 0.735". M70 barrels are very uniformly indexed or timed, making them interchangeable. I have replaced unserviceable barrels with used barrels and all have indexed properly. In the process of re-barreling rifles, I've collected a number of used or unserviceable M70 barrels. On day, I checked about a half-dozen of these in a receiver and they all indexed properly. That is, the extractor slot and sights ended up where they were supposed to be when the barrel was tightened. In addition to "fitting" or indexing, headspace is a major concern. Headspace must be checked when swapping barrels. Most unaltered barrels and actions will probably headspace OK. Insufficient headspace is easily corrected by reaming the chamber--usually only a few thousandths of an inch. Excessive headspace will require the barrel to be set back a full turn and with the coned breech, extractor slot, and sight boss + forend screw to deal with, this becomes a major, and generally, inadvisable job. Bottom line, a pre-war barrel should fit but have the headspace checked.
Roger

Thanks! Bob