How to wire an alternator on a tractor
One of the easiest and best improvements that can be made to an older tractor is to replace the original generator with an alternator. Alternators do a much better job at charging a battery at the low speed tractor engines are usually operated at. Replacing the generator with a GM one-wire alternator is recommended.
Disconnect the negative terminal from the tractor battery.
Fabricate mounting brackets for your alternator. This is the hardest part of this project. You may be able to find brackets in a junkyard that will work with minor modifications. If brackets cannot be found you can make them yourself using 1/4-inch flat stock steel, about 1 inch wide. Mount the brackets using the original mounting holes in the engine block for the generator bracket. Make certain the pulleys align properly for the belt and that the bracket allows for adjustment of the drive belt. Install the alternator and new drive belt.
Using 10-gauge wire, to which solderless ring terminals have been installed, connect the output bolt on the back of the alternator to the positive terminal of the battery. You can also make this connection on the starter solenoid where the positive cable is connected. Follow the positive cable from the battery to where it is attached; this will be the starter solenoid.
Connect the battery negative cable.