I'm not sure what kind of an HEI you are using. When I hear HEI, I think of GM's ignition systems that have the coil built into the cap. Yours must be different if you are talking about an external coil (although I think early GM HEI units had an external coil). My HEI has two external connections...a B+ (to ignition) and a "tach" connection. You need to verify this but I'm guessing your pink wire might go to the +ve side of your coil and the black to the -ve side.