I am no expert on electronic systems, but I have been told that if you have a strong spark there may be no need for a box unit like a MSD 6. I have a MSD 6A on my 57 (came that way), MSD coil and a Pertronix Ignitor distributor kit. Every thing works real well together.

On the other hand, on my 34 I have a GM HEI with coil, and no MSD (or other) ignition system. Again all is well. I was thinking about putting a MSD 6A on the 34, but a mechanic friend told me it would be a waste of money because it just was not needed. He said that if I had to have it, go get one, but recommended I spend the money on something else. (probably him )