I'd cut off this expanded history with the last pre-Byrne issues; the few issues between "Crisis" and "Man of Steel" may not technically be the Superman of Earth 1, but then Fleischer's book treated him as one guy from 38 to 64 anyway.
Superman# 423 and Action Comics #583 should be the cut off points for this.
And I agree. The cut-off point should be just prior to the events of Crisis on Infinite Earths.
Super Monkey and Bill 9000, you guys are actually talking about two separate cut-off points as if they are the same: There's "just prior to Crisis" followed by, about a year later, Super Monkey's S 423 and Act 583, the "last pre-Byrne issues."
I don't really know which cut-off I'd pick. The time between Crisis and Byrne was a sort of grey twilight dimension, that continued a Superman continuity that was much like the Earth-1 Superman's continuity, but with a number of stories that don't really fit and perhaps shouldn't be included. Stories like
Crisis, the last issue of
DCCP, and Supergirl's secret marriage. So maybe the cut-off should be just before Crisis. But then we'd be cutting out some Bates, Maggin, and Swan and one could make a pretty good argument that their stuff is
always canonical.
On the other hand, I don't think we can just pick-and-choose some stories and not others from that final year. So if I had to pick (which I don't
) I'd side with Bill 9000 on this and cut it off right before Crisis - sorry Beppo and Nightwing - I don't think Crisis itself nor that last year of pre-Byrne stories really fit.