Fluctuating neg. to ground on ignition coil

I actually live near one of the most well assorted US cars parts stores in Sweden, so I can pick one up easy, but they sadly have no specifications on the resistance, so I might end up with another one, with the same specs as the one I have, well well...

From their cataloge:
View attachment 1715531534
STM almost certainly = Standard Motor and part number is RU12. Same as on the truck now.
More Information for STANDARD MOTOR PRODUCTS RU12