Yes, and no. I won't run 430s (or higher) in the Mach, as they would inhibit my driving on the twisties. If I did more 1/4 runs, I'd switch in a minute.
None-the-less . . . yes it stinks a ZR1 can beat a GT at some places. However, FMC and Multimatic built the GT for a specific series, as noted above, to the limits of the regulations to race for a certain number of years in GT2. The street car is a by-product of the race car, plain and simple . . .