Chris: I agree with beez. I also use the 235 and 265 Cups, but on OEM CS rims. The 285/30 Cups should fit your 10" rims fine, but then you might have to do something about additional understeer (push).

The RA1 245 and 275 seem to be better sizes for your 8.5 and 10" rims, although I don't know if they will actually work (grip) any better than the 235 and 265 Cups.