We just use one group 31 in the battery box beside the stater on 4430s and a 4250. We made new cables and use stud post ends cables are very short. They seem to start just as well and last as long as the 2 6volt setup plus elimnate the batterry cable under the cab., also a lot cheaper. I use 2 group 31s in my 8650s but they are a lot bigger engine.I really like the stud posts and with one battery I figure I can even replace them more often and still save money. I buy them at my KW dealer.