The ballast is not necessary if an MSD 6 or 7 series Ignition Control is being used with the points distributor. When you are using an MSD Ignition Control, the ignition is responsible for delivering the voltage to the coil so a ballast is not necessary.
link (http://www.inlinefour.com/twincamtech/msdblas2coil.html)
C.T. :wink: