Hi,
in general I would prefer the late 70's. But that depends on the grade of model. The higher grade models of the late 70's don't have a chambered body. Better ask for the models (if the sticker on the back of the headstock still exists) and the serial numbers. I think they started with the flower pot inlay on some guitars around 1985/86, the serial number would help to identify.
Regards
Volker