Transistorised, breakerless ignition was used.
I just had a quick flick through the SAE papers on the 427 engined car & it states that this type of system had proved its self previously on the ' Indy 4 cam ' and 289 race cars.
will get you a copy of the entire set of papers, and in that you will find an article on the ignition system including some pictures if I remember correctly.