Here's some information from the left coast.
Track records for ITA, ITB and Pro7. Pro7 is close to an IT RX7. A bit less tire and HP, but close.


Willow Springs: (HP track)
ITA ITB Pro7
1:34.7 1:37.6 1:38.2

California Speedway: (HP track)
ITA ITB Pro7
1:57.0 2:03.0 2:01.6

Buttonwillow: (Handling track)
Config 25 CCW
ITA ITB Pro7
2:09.1 2:11.4 2:11.1

Config 27CW
ITA ITB Pro7
1:17.4 1:19.4 1:20.0

So I think a IT RX7 in ITB would be close to ITB, may need a bit of extra weight.

-chuck-