I concur with Norman’s recollection. My impression is that 3/4″ 6 gauge screws were the usual standard at that time (for securing the plywood to the framework), but nowadays that size seems rather large, and I would naturally think that 5/8″ 6 is a better size. That is not necessarily passing comment on the choices made by the builders of that era; I don’t think 5/8″ screws were readily available then, but I think they are now.
That is always provided that either the screw holes of the frames and stringers are in good condition or alternatively that you are drilling and plugging them to give a good new substrate.
Oliver