Take a close look at the front calipers, 05-10 on a base model that was 5 lug. Smaller piston and caliper bore? I have seen 2 different "large" rotor caliper bore sizes and attendant large/small pad sizes. Pad size appears to be dictated by caliper bore size. I am using large on the front and small on the back.(My car is only "slightly Goblin" and I am using ft steering knuckles front and rear.)
I have stripped several donors, 08 HHR(5 lug discs ft/r. Sadly I failed to collect these rears), 06 base Cobalt (4 bolt disc/drums), 08 Co(5 bolt disc ft, no rears on car) I do not have a front or rear caliper example that mounts like the Solstice rear disc/parking brake style. Though another car line may use a similar caliper? Look at the Pontiac G6 and the Malibu, likely donors IMO.