I do not know what type of alternator you have fitted, but 13.2V doesn't sound enough to fully charge battery, I would be looking for 14.2V.
On a mass produced car I would suspect the internal voltage regulator in the alternator, on a Morgan I would also check that adequate size cables & earth leads had been used when the car was built.
There were both these faults on our 4/4 when we purchased it, service records showed that garages didn't spot the problems and just sold the owner a new battery every year!
