Pavelich,
1-Do you plan to do much if any dry camping or real boondocking?
2-How big is the space for the house battery?
For 1, if the answer is no or very little, a large single jar (like a grp31) might be just fine.
If you think you might need more, go to 2:
If you can, measure and see if you can fit in 2ea GC2 (golf cart batteries). You will need a cable to make them in series for 12V. These are real (but less expensive) deep cycle batteries. If you drag them way down, but recover them promptly, they will not be damaged as much as non-deep cycle jars.
Matt