Thanks MikeIf it's a standard lead acid 8D it's not deep cycle. Deep cycle are designed to be heavily discharged between charging's, like in a house application where cabin uses bring them down to low voltages. They can then be charged with no damage or loss to their original capacity over and over. Their downside is they do not provide the cranking capacity a cranking battery does and on a new engine installation review deep cycles for starting will fail engine warranty requirements for the companies I worked for. A starting battery provides much more cranking amps but can't recover from deep discharges like a deep cycle. As for engine cranking a lead acid 8D is very hard to beat. Probably the best starting battery available, especially for the money. 2 good ones will crank a 15 liter Cat for a long time even in the winter.
On my desk I only have B /C Cummins requirements handy. They require a minimum of 2 Group 31 lead acid batteries or an 8D.
My boat with a B has 3 Group 31's and I have no trouble running them 7 seasons and change them out only because they're getting old. I haven't load tested them but they hold 12.2 volts over the winter with no starting issues after 7 years. The third set will be going in this spring. With all the EPA stuff the last 15 years there's not that many battery manufactures around anymore. Most likely whatever label you choose it's probably an Exide or East Penn. They're both good but batteries have gotten expensive especially when you up for the better in a particular Group size. I got a quote for the 3 in the boat from my local battery warehouse and it's up around $50 each. But the little 24 for the minivan was almost $90. I bought it anyway as the van was down but later checked and Walmart wanted the same amount.