Guys here is some info on small sealed batteries. I would use the ETX 30L group size. If you can't get a CARQUEST battery, try Oreily's they sell East Penn batteries as well...also sold as EPM brand. We are OE on every Harley manufactured. The ETX 30L is for the big Harleys and I have personally tested it to the 550-565 CCA range. Same exact size as an Oddesy PC925...only more powerful. Personally tested
Whatever you get, make sure it is a Sealed AGM design. If it comes with acid it isn't AGM. AGM, Absorbed Glass Mat. The acid on these batteries is injected under vacuum so that only a certain amount of acid goes in the battery. It is then sealed.
AGM batteries can be deep cycled, charge 50% faster than flooded wet cell bateries and are much more resistant to vibration.
Here is the link for more reading. Good Luck!!
http://www.thesamba.com/vw/forum/viewto ... ht=battery