Hi Tim,
Apologies for the late reply.
I spoke to one of the specialists at First National Battery (factory) yesterday.
Seems like OEM spec for early Gen3 diesel LWB was only 60Ah - I prefer the 70Ah - but as noted at the end of the day you are looking for available amps at crank.
The spec on the 652AGM is 760A cold cranking.
AGM technology apparently also gives greater deep cycle performance.
The spec on the 652C Sealed Silver Calcium equivalent performance is 400A cold cranking.
Explanation of some battery specification terms here:
Automotive Battery Specifications Capacity / Performance Definitions
Hope that helps.
In the meantime my 652AGM just died after 2 1/4 years (will find out tomorrow if its terminal - 'scuse the pun) - maybe too infrequent use, too short trips - will probably invest in a smart charger to look after the resuscitated or replacement battery and hopefully extend life.
So we can add to the two sure things in life:
Death, taxes and (if you own a Pajero) running costs.