I had an old Don Hardy , east texas race cars vega , w/ dual battery boxes flush mounted below the floor ,it had an all alum. interior tho. Should be easy to do in a big car , I`d think.
its funny, its not that big of a car...there's less real estate here than most would figure. parked next to my dart, its honestly not a ton larger...my wifes 4 door charger Dwarfs it!
when we did the cage and mounted the fuel cell, my buddy originally bolted it in behind the license plate, but its pretty impractical there though. it fit...but god help ya if ya needed a jump or or went to change it lol it may end up in the trunk after all. part of it being that the full tubs kinds of rules out anything outside the frame rails.