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!
Jack is correct Paul. 13.2 volts is too low unless the battery is so depleted the alternator hasn't been able to bring the battery up to that voltage yet. It's also what would be expected from a smart charger in float mode after the battery was fully charged at a higher voltage.
The charge voltage is best monitored after the starter has been used on a previously fully charged battery. The alternator should quickly replace the energy used to bring the battery back to full state of charge and will require in the order of 14 + volts and as much as 14.6 volts to do that. This assumes battery (despite being new) and alternator are performing correctly.
As well as faulty components an unforeseen and uncommanded battery drain could cause the issue so check for any partial shorts, cables getting hot etc.
Finally bear in mind that the alternator is regulated to provide a maximum charge voltage around 14.4 volts but its the battery and other loads that control exactly what voltage it puts out once working flat out. This means it could be less than the afore mentioned for a short while and particularly if alternator is simultaneously satisfying other loads such as lights, wipers etc.
