Model airplane landing gear wire comes in a few sizes, and is available stainless. You can drill the edge of the pad backing for the ends to stick into. Bend a V with right angle ends to stick into the holes. Size of the V determines pad push back. Two Vs per pad set, springs are under the caliper on the outer edges of the pads.
You can size the clearance by stacking back shims so that your new pads wont retract farther than your hydraulics can take up. If you run rear brakes only (we used a hand lever because pedal space gets small quickly), you can connect both portions of a dual master cylinder to feed a single line. It moves enough fluid to handle drums or disc in the back. If you can size the clearance correctly, at retraction, you can run the springs stiffer.
Food for thought...a well planned handbrake is really useful when hand moving (or winch loading) a car. If it can be reached from outside the car, all the better. Also makes one less pedal in the footwell when cleaning out the salt between runs, and less leg movement needed for leg restraint control planning. Remember...your right foot is hooked in a toe return on the throttle pedal. I'm not a big fan of footbrake on the salt, as you can tell. Even my next bike project will be handbrake and hand upshift on the handlebars.
