It can be done. Both bikes have electromagnet alternators. However, the wire colors won't match, because on old vibrating point type regulators like the old 750's, the regulator is wired on the power side of the alternator's field coil, while on electronic regulated systems like the 650's, the regulator is wired on the negative side of the alternator's field coil. I can help you with the color mismatch if you are interested.