Indeed there are; in fact across the fleet of A319s there are aircraft certified at 62, 64, 66 and 68t. Also not all of the A320s are certified to the manufacturer's MTOW; off the top of my head, some are 77t, some are 73.5t and I think there's some with a different limit.
Chadwicki, if you're interested, at the moment you're on G-EZTN.