cruiserbrett
GOLD Star
Interesting. The rotors can not be any thicker or they won't fit in the standard GM caliper.
you could always get up really early in the AM, and head to the junkyards and if you are lucky there is a GM car that just showed up with the right calipers that still has the clearanced (read:used) pads in it...

On a more serious note, I cant see how a thicker rotor would work either. As it is, with the common rotor, caliper and pad combo for rear GM discs there isnt a 1/16th of an inch clearance.