Rotary switches control the digital circuitry inside the distributor, so you can toggle between 27 pre-configured centrifugal and vacuum-advance curves without messing with springs or weights. You don’t even have to twist the distributor body. We set ours to deliver a full 35 degrees of centrifugal advance by 2,800 rpm (switch setting 6) to suit the Dart’s 3.91:1 gears, 3,500-rpm-stall speed, and 2,800-pound weight. Likewise, rotary switches built into the Crane allow setting the rpm limiter. With its low-mass stroker assembly, rev-happy roller cam, and high-speed ignition upgrade, the 512 eagerly pulls to 6,500 rpm, so we set the rev limit switch to 6,800 rpm.