Well, after quite a bit of searching, the only performance tire that I have found so far in my preferred size of 215/60/15 is the Dunlop Sport Classic, for $340 ea. That is way more than I have been paying for my race tires, so those are out.
My current tires, Yokohama AVS 215/60/15, diameter 24 1/2", were great, but have no direct replacement. I want to get as close to that size and performance as possible.
My short list from TireRack as of right now is:
Yokohama Advan Fleva V701, 205/55/15, diameter 23.8, $126.76 Good reviews from Miata drivers, which is pretty similar in weight and performance as a 240Z
Toyo Proxes R1R, 195/55/15, diameter 23.5" $156.47. Lots of good reviews on various sports cars.
Yokohama Avid Ascent GT, 205/60/15, diameter 24.8" $114.99. No reviews on TireRack on sports cars, but got a strong recommendation from Ken above.
So, it looks like my choice is either more documented performance or closer to my preferred size with one personal recommendation.
Hmmm, decisions, decisions....