12 team, 162-game schedules
2 leagues, 1 division per league, 6 teams per division
(or 1 league, 2 divisions, 6 teams per division)
90 games versus own division (18 per opponent)
72 games versus other division (12 per opponent)
Along the vein of recent discussion, here's a group of 7 schedules, one for each "Year Starts On" day. Also included is gmo's chart for accurate "Year Starts On" days.
I think I took the 1986 schedule w/o doubleheaders, deleted the AL, and then juggled a few series around to break up the longer road trips and try to reduce my pet peeve, two game road trips/homestands. (I also have gmo's 24 team, 2/2/6 schedule lying around, so I might have started with that one.

)
The only quirky thing is one team in league/division 2 makes a "tour of the division" in late September, visiting every park in 3 2-game and 2 3-game series. I decided I could live with that, considering some of the 4-series-long trips have more games than this.
Big thanks to LGO and gmo for doing 95% of the actual work involved.
