There are a couple of differences between the pre-64's and subsequent models, which are worthy of mention. Before I get to that, I should mention that there are sub-sets within the pre-64 category. The pre-war, with clover leaf tang and wing safety which pivots about 120 degrees and swings over to the left side, the transition model, which retains the clover leaf tang but which gets a safety which is located on the right side and does not have to swing under a scope, and the later models with full tang and right side safety. There are noticeable differences in quality of manufacture as we pass the mid-fifties. Now, back to the differences.
The first difference is with the bolt, which, in the pre-64's, has a one-piece body. The handle is integral. Post -64's have a handle which is a separate piece and is brazed on to the rear of the bolt body. The second big difference is in the magazine and feeding system. The feed rails on the pre-64 are machined into the receiver. The magazine box is straight sided. The post 64 box forms the feed rails and the top of the box is folded in to form, in conjunction with the receiver rails, the feeding system.
Another difference results from the cartridge for which the pre-64 was designed. The pre-64 was design for and around the 30 Gov't 1906 cartridge; the 30/06. Modifications made by the factory to accommodate the longer H&H magnum cartridges, weakened the action. The post-64 action is longer and designed to be able to accommodate these longer cartridges. There are other, less obvious differences which were made over the years. Changes to the bolt stop, to the firing pin, bolt sleeve, and more than anything, materials and the methods of manufacture, highlight the differences between pre-64 and post-64 offerings. I like Winchesters and especially the pre-64's. They are representative of one of the best designs the North American industry has produced.