Venting trunk mount battery?
"Need." What a word, LOL
If this is anything aside from an Optima look alike, it SHOULD be vented, and MUST if you go to any race outfit.
ANY conventional battery produces explosive and corrosive fumes. "What this means" is that anything in the trunk is open to attack, AND it's an explosion hazard.
By the way, NHRA won't approve plastic boxes unless you have a firewall between the trunk/ back seat.
Venting CAN get "Pretty Red Neck." One "redneck" way would be to put the entire battery into a heavy plastic bag, and tie it tightly around say, a piece of heater hose run through a fitting in the floor trunk.
Otherwise, "some batteries" can be provided with caps with vent fittings or maybe "get out" the JB weld LOL
Somebody claims these were used on Corvairs
http://www.corvairkid.com/images/Delco_vented_caps.jpg
http://www.restorationbattery.com/r59s.html