HEI conversion time...

On the far end of the scale, this is what you can get away with. The former owner had a Mopar ECU mounted here on the flat between the heater and wiper motor. They had already penetrated with on small sheet metal screw, so I used on of those holes and drilled another. I did use thermal grease, and had intended to add a separate ground lead under the screw holes, but just the other day I checked the ground integrity and it's OK.

B+ and the tach both come off the coil terminals. I've run this coil now through 2 summers with no ballast, a stock Mopar coil, with no ill effects. On a simple, mild, low compression street engine I see no reason for the fancy, expensive, E core and other "big" coils.