Reply to "Battery drop down Box"

FWIW, you really don't need a battery 'box'. When I did our battery a decade or so ago, I made a crossmember of 2" aluminum angle, bolted between the front subframe rails and floor; the battery sits on top of it. No fumes or corrosive liquids can build up and the crossmember may even add some front stiffness. The battery is restrained by the firewall which is right at the back edge of whatever hole you cut. The front is bounded by the triangular rack mount- which incidently is only about 6-1/2" away so square batteries just won't fit, box or not. The left side of the battery is restrained by the steering shaft and clutch hard line. I added a rubber tie-down strap and a short piece of wooden 2x4 to restrain the battery from sliding the extra 2" towards the right side. No evidence of any battery motion in 30,000 miles.
A stock 'hot' battery cable reaches the area by rerouting it under the floor; a std ground cable now bolts to a rack-mount bolt. I added a sheet metal cover held on with 2 dzus fasteners. For dropped batteries, I recomment top-post units 'cause side-posts get very close to the rack mount or the firewall; dual-post batteries should leave the side-post block-off plugs in place for short-circuit protection. Rubber post covers add some extra upward protection if you routinely 'get air' or hit big bumps at speed.
And while you're doing all this, reroute the front brake connecting line from its stock position behind the battery to under the floor. When you do this, you may be surprised at the amount of corrosion on this vital line from being right next any battery leakage, protected only by a thin plastic sleeve- that's usually torn. Besides being safer, it also tidies up the front compartment.