Well the battery in the car finally gave up the ghost. For those of you who may have the same question as to which battery/s fit, the one I took out is a Die Hard 30325 Weather Handler from Sears.
I replaced it with a Duralast Gold 25-DLG from Autozone.
I'm not even sure what the original battery specs were, but the Die Hard had 480 cca and the Duralast I put in has 610cca.
Now if the battery dies while you are driving I was always under the impression it would continue to run until turned off, then it would not start again. However this one died while driving. Is that common among MG's?