I'm in a single-season twist (based off of the 500-HR club) in which the division leaders right now are from:
1988
1991
1941
1995
1996
1917
Of course, there aren't many deadball-era teams because of the nature of the theme.
In a similar theme (this one based off the 3000-hit club, of which there are several deadball-era teams), the leaders in the most recently completed season were from:
1984
1960
1979
1982
1983
1959
In the most recent version of finn2030's bookend twist league, there were plenty of deadball era teams, and some of them won divisions because the alignment was chronological, but in the WS a Mario Soto team beat a Tyler Houston team. I used a Nat Hudson team (19th century) and they were under .500.
Tough for me to see deadball domination here. In fact, because of the fielding problems (and limited rosters) that deadball era teams have, I tend to think they do poorly in these kind of themes. Of course, deadball era pitchers are still very dominant in OLs, but that's a different question.