Usually all the grounds are bad on anything perfectly painted and restored to the Nth degree.
Sometimes Folks are shy about sanding off that perfect paint to create good grounds.
I'd definitely look there.

Look at resistance from engine ground to battery negative.
I'd check for 6 to 9 volts at coil + in "run", 12+/battery voltage in start.
Check coil primary and secondary resistance, also check continuity from the case
to the windings as any sort of a circuit found there constitutes a shorted coil winding.