I'm thinking 285/35-19 in the front is the way to go (close to eom diameter). Problem is finding rears that are close. I think the solution may be to go with 20's on the back.
285/35-20 or 295/35/20.
As is happens the 285's are both available as goodrich g force rivals.
Ditto bluebeast. Not sure why people would argue this point. Maybe they remember the Pinto and its "road hugging weight".
Anyways OP, you probably should have posted in the drag, track, autocross forum where people care about these things. I agree such an option would be nice but as others...
Your friend is correct. Most awesome canyon roads. In fact once you get south of Glen Rose you can take awesome two lanes roads the whole way down. I would recommend Kerrville as a base camp. This trip is good alone or with a group.
You say the z28 won not by normal means. I guess we don't know what that means. Taking two tires is just a strategy. Sometimes it works, sometimes it don't.