1958 Ford 861 Tractor

So if you check for power to the negative side of the coil with a test light ground to the positive of the battery you have power with the key on ?
If no power,check ignition switch.
If you have power,attach the test light to the negative side and have someone crank the tractor as you hold the test light to the positive side and it should blink as your points are opening and closing,,,Is so,then your coil is bad!!!
To test coil since it is positive ground,disconnect all wires to coil,run power to negative side and run a attach a ground to your block,have coil wire with in sparking distance of the block and tap the positive side with your grounded wire and that coil should spark every time it is grounded it is what your points do...