I used a Powermaster AGM cell behind the dash in my 5 window. I used a panel mounted on the inside of the firewall that attaches to long 1/4x20 bolts through the holes for the dash tunnel that I am not using to mount all my wiring. I made a hinged battery tray that will drop the battery down for service. Th AGM cell is very small but has 550CA spins my Flathead over just fine. The battery is above the steering column.