[What's the better investment, the 70s mod 70 or a new one???]
It's well known that, in 1964, Winchester made drastic, almost unacceptable, changes to the Model 70 - so unacceptable that they eventually caved in due to poor sales & upgraded the lousy stocks, impressed checkering and other cheap parts starting in the early 1980's, culminating in the pre-64 clone 1991 Model 70 Classic.
The very best was the 1991 M70 Classic Super Grade, which was the year that had the stock designed by a good custom stockmaker.
Later Super Grade stocks were desgned by a custom stocker, too - but a different one - and they look a little differently shaped.
A 1991-2006 Model 70 Classic ( CRF - controlled round feed) would be preferable to a 1964-1983ish push-feed.
FYI - pre-64 M70's were all CRF, in 1964 all were push-feed until the CRF Classics introduced in 1990-91 (IIRC), at which time both types were offered until production stopped in 2006.
You said "new one". I have no knowledge of the new (2008) Winchester FNH Model 70's, as they're not expected to hit the marketplace until early next Summer.