I thought about using new hubs to allow for bigger tires but you have to be careful to get hubs with at least a 5x4 1/5" bolt pattern. The hubs with a 4x4 bolt pattern are only for 8-10 inch wheels.
Well, for $4 more a hub...
http://www.surpluscenter.com/Wheels...l-Hubs/HIGH-SPEED-WHEEL-HUB-5-BOLT-1-1134.axd