Now that you have your tractor back to a running state...
The pertronix 1442 is the correct electronic ignition module.
The factory coil works fine, but you do need to make sure that it is above the resistance requirement for the pertronix. (3-4 ohms if I recall) Too low a resistance may destroy the pertronix.
You do need to set the timing after installing the pertronix module. Use a timing light.