Massey Ferguson Industrial 31, 1973 or there abouts. The regulator has 4 wires, the alternator is new not rebuilt and has 3 wires. Battery, ground, and field. I think the current regulator is from a Ford car and since this is a diesel I don't think it will work. It has a 4 cylinder Perkins engine, the plate on the engine is unreadable but it starts with A4 xxxx. Trying to identify the engine I am guessing it is a phaser/1004 series. Am I right in assuming Diesel regulators and gasoline engine regulators are not inter-changable?