David Ross has one (an ITS Z31) here in NC somewhere. Very well prepped and fast car. Runs good times at VIR, and I think led a race at CMP a few years back. It was for sale recently for less than $10k, not sure the exact price though.
Also, I believe Grayson Upchurch's car is still kicking around the Atlanta area somewhere. It won an ARRC in the mid to late 90s before the RX7/BMW onslaught began.
I think the Z31 makes a decent ITS car, although it is probably not THE car to have. However, with the impending move of the E36 to ITR, ITS may be more wide open than in the past.
As the posters above indicate, Z32 300ZX is anticipated to be an EXCELLENT choice for ITR, but who knows how it will pan out?