Hi David
My superseal has a Beta 14, which must be similar.
When I replaced my starter battery a couple of years ago my main consideration was that the new one should fit the space the old one occupied, so armed with the dimensions I visited a car battery supplier (ATS I think).
The second requirement was sufficient grunt to turn over the diesel engine.
I purchased the right size which happened to be the battery fitted to a Mitsubishi Shogun, so I recon I got the power right too.
It has performed fine, the key is to not let it run down.
I hope this helps
Philip
rascal