Multiclass as a Bbr1/Clr1/FtrX. For cleric, choose Kord as your diety (with the Strength and Luck domains). Strength domain allows you to cast Enlarge Person as a domain spell. And if you are allowed PHBII, then you can take the alternate Cleric class ability to spontaneously cast spells from one of your domains instead of cure spells (obviously for Enlarge Person, as you can't prepare Enlarge Person in a non-domain slot as it isn't on the Cleric spell list).
Feats are mostly obvious - Improved Grapple, Improved Unarmed Strike, TWF, Wpn Focus/Specilisation grapple (and/or unarmed strike, depending on your flavour), Power Attack.
Complete Warrior has some additional grapple-based feats worth considering, like Earth's Embrace.
But also consider Stunning Fist, if only to get access to Weakening Touch (CW).