To be honest, they didn't have to have a 5v setup. there are ways to have conditioned the old style signal to be compatible, but it was cheaper to go the way they did if they were already adding a bunch of sensors and such that used 5v. I am putting a dual TBI setup on my 51 Plymouth's flathead and am using the old school mopar electronic ignition distributor guts from a /6 in my 51's distributor as the ignition trigger.