MississippiRifleman:
THE standard ref's on the Pre-64 are Rule's RIFLEMAN's RIFLE (now back in print) and Whitaker's THE WINCHESTER MODEL 70 (out of print). Both will show you the technical differences between the Pre-64 and the current CRF Model 70's.
The REAL difference between the two rifles is something that you'll have to experience by comparing the two in your own hands. The optimal pre-64's were made prior to 53 or so before machinery was wearing and costs became a problem and quality control lapsed over the last years.)
Personally, I find a major difference in quality in the older weapons and have seem and heard of too many current iterations with feeding problems, gross tool marks, bolt faces apparently fit with cold chisels, etc. Owners of the current 70 and many of the gunwriters will tell you the new iteration is THE best yet. Opinions and orifices, you know......
Check the older ones out before you make a decision--if you want a hunting rifle that you and your grandchildren (assuming the politicians of the clintonista ilk don't ban them all by then) can be proud of, a nice piece that is a bit below the grade optimally desired by collectors can be had at a reasonable price. A little professional work on bedding, trigger adjustment, oil finishing the stock, perhaps adding a Decelerator pad if the calibre requires it, produces a really optimal hunting rifle that puts most other factory efforts to shame.