If your "1 wire" alternator is a Delco SI type with the long rectangular regulator plug at the rear outer edge of the alternator case. (terminals set up like this[- -]. Then there is a good chance it will work with the charge light.
Go in the regulator compartment down in front of your feet, remove the old regulator and make a jumper wire with male blade connectors to jumper the regulator plug terminals at opposite(outermost) ends of the plug. At the alternator, connect the "F" wire from the old square plug in the tractor harness, to the #1 regulator terminal in the new alternator, using an alternator harness repair plug from an auto parts store for any 74-84 GM product. Connect the small white(#1) plug wire to the harness "f" wire at the alternator. Also Connect the larger (#2) red in the new alternator plug to the "BAT" stud on the alternator rear using a ring terminal.
Thats it, the gen light should come on when you turn on the ignition and go off when the engine starts. The alternator is also now wired so any common 3 wire Delco SI alternator will work as intended if the "1 wire " alt ever fails and needs to be replaced.
I did this exact conversion to my 856 a couple years ago.
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