I suppose, in the old days, all the mechanics were trained "in house" under the supervision of an "old foggie" both in dealerships and factory mech. school, experience was the game, people were more mechanically minded, designs from one bike to the other were similar, hence I don't think there's any official records for that sort of things. Things went slightly different in WW2 when distance from dealers/factory was huge and loads were conscripted, not necesseraly with knowledge, hence a bit more details in the WLA/WLC manuals...
As far as street bikes are concerned, the 1st ever H-D Service Manual as we know it is in 1959, and as they say in the front page, "most" herein can be applied to earlier designs!!! Before that, the "Shop Dope" sheets were all that was available... A loose collection of new or improved things the factory thought might be of help to the dealerships.
Most spanners and tools have a restricted lenght designed into them that should prevent overtorquing when used with std hands.