ITA CRX: Tires

[280ZX3]

My race team is going to be running two '91 ITA CRXs next year and we've decided to make the jump from 14x6s to 15x7s. We're currently running 205/55/14 Kumho V710s on the 14s. We're kind of on a budget and looking to get the most bang for the buck.

We would run 225/45/15 V710s, but Kumho doesn't make that size. Hoosier, Toyo, and Nitto do.

The problems as I see them:

Kumho- Can only run Kumhos in 205/50/15s. 20 mm of tread seems like a lot to give up.
Hoosier- $217 a piece. $50 more per tire than other tires in its class. They also don't last as long, but are probably the fastest.
Nitto NT-01 - Are they as fast as V710s? Looks like they probably should be shaved.
Toyo R888 - Same problem as Nittos.

Can anyone give us any suggestions? If anyone has made the jump from 205s to 225s on an ITA Honda, I'd be interested to see how much of a difference it actually made in lap times.

By the way, we're not opposed to the 14x7 option either, but I'm having a really hard time finding any 14x7 Honda rims.