HEI ignition module

You do not need a separate grd wire, as the module grounds to the dist body. The dist clamp is the ground source. Roughen the tabs/feet on the clamp so that they make good contact with the dist.
Mounting the coil on an engine is a baaad idea. Yes, I know OEMs did it [ for convenience/cost ]. The coil has copper windings, a very good conductor of heat. So the coil heats up, & so does the resistance of the copper windings, reducing coil output.