head differences between 81 82 83 750\"s

I recently picked up a 81 750 ltd for dirt cheap. I runs fine but needs to be freshned up. I thought about puting the 810cc kit on it but my question is with the heads. Is the 1982 gpz head any different than the regular 81 kz head or is a 83 head even interchangable with the 81 moter. The most important question is; is it even worth looking into the head swap or should I just keep the 81 head that is on it. Just trying to get the most bang for the buck without getting into expensinve headwork. Thank in advance.