Venting trunk mount battery?

I have a trunk mounted Battery in my 70 swinger and it has been that way for years. However, it has always been sitting on a battery tray bolted to the floor with a battery hold down.

I just added a plastic marine battery box to it with a lid. Do I need to "vent" the battery in anyway? If so, what is the best way?

This is just a regular battery, not an Optima.

Thanks!