With the ignition "ON", points closed, WHAT voltage are you seeing on the primary terminal on the coil that is connected to the ignition switch... if full "12 Volt" battery voltage, you need a coil with a primary resistance in the 3 - 4 Ohm range.
If the voltage measures in the 6 - 8 Volt range, that indicates there's a ballast resistor in the circuit and you can use a coil marked "Use with external resistance".
These voltage readings ASSUME the points are closed and making contact AND the primary of the coil is not "open". In other words, the primary circuit must be intact and flowing current or the voltage measurements will be meaningless.
As to the secondary resistance, it will likely be in the 6000 Ohms to 12,000 Ohms range, measured from either of the primary terminals.
(There will be a tiny variation in the secondary Ohms reading depending upon from which primary terminal the measurement is made 'cause one way the primary resistance will be in series (added to) the secondary resistance.)
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Today's Featured Article - A Cautionary Tale - by Ian Minshull. In the early 1950s my father bought an Allis Chalmers B and I used it for all the row crop work with the mangolds and potatoes, rolling and the haymaking on our farm. The farm and the Allis were sold and I have spent a lifetime working on farms throughout the country. I promised myself that one day I would own an Allis. That time event
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