For the most part we've found if you have a good starter, a single one of the new 1000 amp at 0 batteries will more than replace the old 2 six volt batteries. One large battery is also cheaper than two six's.

I've changed both my 2-110's to single batteries and have no problems starting them. Go ahead and convert your cables to stud post while your at it, a LOT less problems than the old lead terminals.