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 - On the Road with Dave Gohl: Tractors and Farming - by Dave Gohl. I never thought I'd live to see the day, when I could call myself a farmer. What allows me to say this? Well, when our family moved to our 20 acre site near New Prague, Minnesota, I had one thought in mind. You guessed it, farm it somehow. A little history is in order. In my younger days, mom, dad and my brother made frequent visits to dad's youngest brother Pete, who took over the home farm from grandpa MIke. It was the typical set-up, milk cows, pigs & chickens. In the winter, we'd play
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