I used this system for 20 years on one of my racing engines. It was 12 volt and use one of their "box" coils. If you find one of the plates make sure you get the outside condenser which is getting harder to find. If staying with 6 volts any coil will do but VW 6 volt were known to be very good. I'm not sure you will see much improvement by just having dual points on a stocker.
If you can stand the look of it; a guy on E-Bay sells converted HEI's for Chevys and GMC's. There is also a guy in Yerrington Nevada that converts just about anything to an HEI or to power an MSD. Up to 3600 RPM a MSD is a super ignition.....Good Luck
