The only pre 64 Model 70s I have owned were both 308 Featherweights. One 1954 model, was in 98% condition, never even had a scope mounted on it and too good to shoot so I sold it. The other of 1953 manufacture, is one of the most accurate out of the box rifles I own:
Coincidentally, the '54 is up for sale on a Canadian gun site by the new owner for good money.
Why so few on the market? People keep them and hunt the rifles I suspect.