Human Barbarian 1/Druid 6/Wizard 3/Warshaper 2/Frenzied Berserker 1/Bear Warrior 5/Mystic Theurge 2
Take the required feats and Natural Spell, and then choose whatever you want for the other three.
When you want to nova for ridiculous strength, do the following:
Wildshape into a Brown Bear: 27 strength
Mophic Body: +4 bonus to strength
Cast Bull's Strength: +4 Enhancement bonus to strength
Cast Enlarge Person: +2 Size bonus to strength
Cast Rage: +2 morale bonus to strength
Rage: +4 bonus to strength
Frenzy: +6 bonus to strength
Bear form into a Brown Bear (again
): +16 bonus to strength
for a grand total of 65 strength