Maybe the best format for 3 divisions is to split up the west coast schools.
North Division - Wash, Ore, Neb, Iowa, Minn, Wisc
South Division - USC, UCLA, ILL, NW, Pur, Ind
East Division - MSU, Mich, OSU, PSU, Rut, MD
Then have all the west coast schools have fixed cross-overs so that they all play each year.