A modern battery should never leak: all quality batteries use some variation of a gel electrolyte and a glass matt to hold it.
Put that in a polypropylene case and the only place anything can leak is from the air vent if the battery boils.
Boiling can only be caused by over charging, due to poor regulation of the alternator output.
Morgan specify batteries from Uni Bull in Austria: they have all the required features and are leak-proof if used normally, as I'd expect the Optima will be. Neither are cheap....
Battery technology has evolved a long way from black cases with removable caps that needed topping up regularly.... and it continues to evolve. The days of lead acid batteries are numbered, it won't be long before some form of Lithium Ion battery is available at an affordable price. At the moment they are over £1000.....!!
