I'd do it this way:
OPTION A: 6 divisions of 5 teams
EAST: BOS, NYY, NYM, PHI, BAL
SOUTH: WAS, ATL, TBR, MIA, KCR
NORTH: TOR, PIT, DET, CLE, CIN
CENTRAL: MN, MIL, CWS, CC, STL
SouthWest: TEX, HOU, COL, AZ, SD
WEST: LAD, LAA, OAK, SFG, SEA
Schedule:
vs own Div (4 teams) x 18 games= 72 games
vs own conference (10 teams) x 6 games= 60 games
vs other conference (15 teams) x 2 games= 30 games
Option B: 5 divisions of 6 teams (no AL/NL or 2 conferences):
East: TOR, BOS, NYY, NYM, PHI, BAL
South: WAS, ATL, MIA, TBR, TEX, HOU
North: PIT, DET, CIN, CLE, CWS, CC
Central: MN, MIL, STL, KCR, COL, AZ
West: SD, LAD, LAA, OAK, SFG, SEA
Schedule:
vs own div (5 teams) x 18 games= 90 games
vs 3 other divisions (24 teams) x 3 games= 72 games