I've always thought that the A320's highest MTOW option is 77 tonnes. However, it seems that Airbus has quietly introduced a 78 tonne version. It's listed in the weight charts only, not in the payload-range ones.
See page 29, WV015:
Can anyone confirm this?
BTW, it's odd that IAE V2500-A1 engines seem to provide about 150 NM more range at max. payload than the newer -A5 version. See pages 50 and 51 of the above document. Can anyone explain?