Gary, I looked up the rating as you suggested and it stated Workhorse supplies a battery rated at 690 CCA at zero degrees. There is also a nice chart comparing batteries CCA abilities related to temperature.
The chart (on page 58 of the Workhorse Owners manual) shows a a full-charged 405 CCA battery at 80 degrees has a 880 CCA listing, at 32 degrees has a 598 CCA and at 0 degrees has a 405 CCA.
Since our travels are within the areas that don't go to below freezing when we are traveling I think we should be okay with using the battery in question. I also keep all the batteries fully charged during storage at home.
2003 Itasca Suncruiser 33V
8.1 GMC, Workhorse, Allison, Koni's
2004 Honda Element toad