It appears that Sam's Group D batteries are starting batteries, as they mention only the CCA ratings.
If you have used lots of cycles of house battery deep discharge, maybe your Group D batteries are not up to meeting that type of demand?
If you have the space, you could just go to two 6v Golf Cart batteries which would provide about 200+ AH of storage at 12V or four of them to achieve 400+ AH storage.
One 8D storage battery will provide about 220 AH of storage. (If they indicate CCA ratings they will likely be 8D starting batteries.)
Costco has GC batteries for less than $100 each at our store.
1995 CC Magna #5280
C8.3L 300hp Cummins, 31,000lbs