My first car was a 1959 sit-up-and-beg Ford Popular with a 3 speed crash gearbox, cable operated drum brakes and yes, 6 volt positive earth electrics.
I would have thought that you could source a coil from something like this - cos I think your best bet is a temporary fix involving taking the original coil out of circuit and using another one in it's place. Should be easy enough to modify the primary connections shouldn't it?
Jools
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