[folivier]

My '93 which was 39' had 2 8D batteries on each side of the engine, driver side was house, passenger side was for the engine start. I didn't have an additional set like yours (mine had propane heat and stove). But I did have a narrow compartment like where your other set is. The corrosion is typical of lead acid offgassing over years.
I repurposed my narrow compartment using this toolbox: http://newellgurus.com/showthread.php?tid=358
Might give you an idea of adding a toolbox.