The 1010 to serial number 51039, had an ignition resistor built onto the key switch. From serial number 51040, there is a resistance wire made as part of the harness. During cranking, the resistor is by-passed in the key switch, so that full battery voltage (the voltage during cranking will be less than 12 volts) is supplied to the coil. When the key switch is returned to "RUN",the resistor will limit the voltage supplied to the coil to about 1/2 of the battery voltage.
As to your problem, We are presuming that the battery is charged, the starter is in good shape, the contact points are good, the point gap is correct, your condenser is good, and your distributor shaft bushings are good.
If the tractor will start, but not keep running when the key switch is returned to the "RUN" position, you likely had a bad key switch. The fact that the tractor started and ran fine with the new key switch until you shut it off, and then would not "fire" even when cranking, may indicate a defective new key switch.
To find out if the problem is in the key switch or wiring, you will need a voltmeter to check volts at the coil with the key turned to "RUN", and during cranking. An analog voltmeter with a needle, may be more useful than a digital voltmeter during the cranking test, and testing while the tractor is running. With the key turned to "RUN", you should have about the same as battery voltage at the coil - with the points open. If the points are closed, you may not show any voltage at the coil -, since the points are providing a direct short to ground. While cranking, the voltage at the coil + should be at least 6 volts. If the tractor is running, you should have about 6 volts at the coil +. If these voltages are OK, then your key switch and wiring are likely not the problem. If these voltages are not OK, check at the key switch for battery voltage at the "B" terminal with the key "OFF", battery voltage at "F" in "RUN" with the points open, at least 10 to 11 volts at "B" during cranking and at least 8 or 9 volts at the "F" terminal while cranking. If you have battery voltage at "B" but incorrect voltages at "F", I would suspect a defective key switch. If the voltage at "B" during cranking is low, I would suspect poor battery cable connections or bad wiring.