RE: Optima Battery:
I installed a 6V optima in one of my older cars ('27 Buick, not much like our Healey!). I got the Optima because the battery mounts under the floor and is very difficult to check for water, clean terminals and the like.
The first one I had lasted only a year, this car sits a lot and the Optima would discharge very quickly, it was usually too dead to crank after just a few weeks of sitting. The old lead acid battery could sit for months, no problem.
Optima replaced that first battery under warranty, but the second one has the same problem. I have to put it on a charger for a day before I need to start the car. They both crank the engine very smartly, I was impressed with that -- but I find the shelf discharge problem unacceptable, especially for collector cars that sit all the time.
I suppose car may have a current leak, but I really doubt that, there is not much of an electrical system on a '27 Buick. The very sensitive ammeter on the dash shows no discharge when the ignition is off. And the lead acid battery that was in it before held its charge well.
Seems like no one else has this problem, don't know what to say about that. Maybe the 12V units are better?
Bill.