I installed a 123 dissy into the S1 of a friend an can only say good things about it: 123 dissy
My only 1st hand experience on Pertronix is with my '59 Chevrolet 3100 (Apache) with the 235ci 6-cyl engine which came with points. I have no desire to put up with the issues related to points and thus purchased an Ignitor-II which makes it run sweetly. I would not recommend Ignitor-I because Ignitor-II has variable dwell and does not require a ballast resistor.