does anyone know if c3's came with uneven rotor thickness from the factory? The rotors on my 81 vette are fairly thick on the outboard part of the vented disc and fairly thin on the inboard side. The discs are riveted in and so I believe possibly not resurfaced. They measure to as new specification so a little confused.

 

I see no one is beating a path to your question, so I will bite.

Because the rotors are cast, I find it difficult to believe one side would be thicker than the other when new. In a perfect scenario, both sides of the caliper would be applying equal amounts of pressure to the pads. And it would be of no benefit to have inner or outer of different thickness.

Here is my guess as to what's going on with yours.
I would think that the rotor is dead-center in the caliper.
Most of your wear pattern is inboard. That indicates the outboard is not doing its fair share. I bet with a closer inspection, you will note the outer pads are thicker also.
The outboard pistons are not coming out of their respective bores like the inners. To me, this indicates a brake fluid blockage, either inside caliper half or elsewhere.
Those calipers are two halves bolted together. At the mating parting line are "O Rings to seal the two halves. Perhaps there is blockage there or in the passage way to the caliper bores / pistons.

At this point, your best bet is to find the offending calipers, then decide whether to rebuild them or not. Some how you need to find out if the outer pistons are denied brake line pressure.
It also would be wise to drill out the rotor rivets and purchase new. I doubt a shop would "turn" those old ones for you.