Decided to go ahead and change out the batteries now, while they are only starting to go south. These are group 65 batteries at 850cca and a reserve capacity of 150.
I got Group 31 batteries. They are commercial ones built by East Penn/DEKA. They are rated at 950CA and 175RC. I have to modify my battery trays slightly to get them to fit, but they are quite a bit heavier and as commercial batteries, designed for semis, agricultural and earth moving equipment, should be more rugged and last longer than just 4 years. That's my hope anyways.
Plus, they are the same price as group 65 batteries.