@CA Traveler: Great idea about modifying a new box capable of housing the GC2s. I found these
Single GC Box but cannot tell if they are capable of being sealed. I suspect not without some mods.
The other issue I face is access. The batteries would need to be installed into the box and the box slid through the opening and into place due to height restrictions. Still doable.
@MEXOCOWANDERER: Duly noted that Deep Cycle Car/Marine batteries will NOT perform equivalent to a GC2. And AGM is the best way to go.
If these darn batteries were on the tongue it would be a very simple decision.