That does not look like a maintenance free sealed battery. Looks like an 8D, at first I thought it was two group 24s before I expanded the picture.
If that is an 8D that is well over 150lbs and can expect gassing on charge. You can see the screw tops. We use these in big boats (or RVs), always maintaining them. Often we switched to sealed Group 31s or LiFePo, easier to move around and no service needed.
I'd rather have two parallel Group 24s gel sealed in that space. Might fit. 8D around 20"x10" and G24 around 11"x 6" Even if I had to give up some power would not want an unsealed battery in passenger compartment.
I hope I am seeing things...
"Two Reservations, one for US one for PR."