How did they achieve large bolt pattern with small bolt spindles?

a special rotor that is no longer available .

The factory delivered setups were Budd 4 piston disk brakes as used on the c-body car line in 1968. I was the caretaker of a 68 ss dart and the front brakes had been changed over to single piston calipers sometime in it life so could not say for sure what the original spindles looked like or part number used.

I think there was someone here on Moparts that hada set of hubs for this application but no rotors.

I had heard the disk hub came from the 66 Trans Am program. 66 A-body KH disk is the same until 72. Scott Harvey had big bolt pattern hubs made/approved for the 66 T/A cars.

The hub on the 66-72 A-body disk is sort of non wear item. The disk is just pressed to the hub.

Bob Tarrozzi happened to be in town the Spring Fling Speed Festival this year (motorcycle race the next day). He was the engineer assigned to the 68 S/S project. I asked a bunch of questions mostly about his Trans Am and Nascar involvement. What I didn't know was that Tarrozzi was a hands on working member of Harvey's "Team Starfish" race T/A group at Chrysler.

Now I see how a S/S project could get connected with 66 Trans Am parts.