So got the 3/4t Chevy rotors, along with the El Dorado calipers, etc off.
The Caddy rotor has a step down ridge inside the hat.
Looks like I'll have to turn my hubs about an 1/8" smaller to slip fit over the face. If I mount them behind the hub, they're perfect, but I want slip fit.
The e-parking brake is two terminals, reverse polarity to lock down or open up the parking brakes. So looks like a dual pole, dual throw, relayed switch will work well for this. It's a worm drive, so no voltage required to hold, once open or closed.