Was just kidding about turning the axle over....

The tallest firehawk listed is 29.1 in a 15" rim.
The least expensive thing to do is nothing.
The next least expensive thing to do is to put the
rear tires on the front and buy two new bigger rears.
The 255 70x15 tires are $69 each plus UPS

That would get you the taller front tire as well as keep
the rear tires larger than the fronts......

The Tire Rack page for Firehawk sizes:
http://www.tirerack.com/tires/Spec.j...ehawk+Indy+500

mike