[David]

I'm running 255/315 now and have for years. I don't like the heavy feel and tramming on the street so I want to try narrower tires. My tires are coming up on 5 years old so if I change the fronts, I'll need to change the rears too, otherwise I'd just change the fronts and see how it works.

I've never driven a Porsche 935DP or Lamborghini Countach but they ran 205 (or 225) fronts and 345 rears so it's not too odd. And I never read about them being terribly understeering cars. Of course I would adjust my sway bars after tire installation to get a proper test of the new sizes.

Another thought is trying to put the 225 and 275 tires on the 9 and 11.5 wide wheels as they are and see how they work even though both would on wheels a 1/2 inch over what's allowed by the tire manufacturer.