Get Rennenberg's books, or at least one of them.
The "pre-64" 1894 guns were essentially hand-fitted. Not because Winchester set out to build hand-made custom guns, but because quality of parts was so uncontrolled that fitters sat down each day to bins of sears, triggers, pins, levers, bolts, etc and sorted through piles of parts to find "matches". They went from there to filing and stoning and the end result was quite often an essentially hand-fitted assembly. Good for the buyer - not so good for the business. And explains why it was more difficult than it should be to interchange parts from one gun to another in the post-war through 1963.
Lots of manufacturing changes between 1964 and the 1997-98 production, from plated cast iron receivers to carbon and alloy externals to stamped and cast internals. 1984 production changes is a tough read... quite a science!
I find it amazing that over the millions (that is still a lot) made, even the "worst" 94's were quite good machines.