The GTO disc-brake spindles are the same as 67-69 disc-brake Camaro spindles. The 68's had 4-piston calipers, the 69's had single-pistons. As long as the calipers, caliper brackets, hoses, & dust shields match each other, you should be OK. Whichever you have, use your Camaro steering arms.
Bob, were those rotors new or used?