I plan on using a Hot Rod Air AC/heater unit in mine. It will mount behind the dash and only requires the two heater hoses and the two AC lines to go through the firewall. As far as the wiring, I plan on using a Painless Wiring kit and mount the fuse box behind the seat, on the flat section of floor where the gas tank use to be, and let the wires run out the bottom and along the frame rail. This way, all the wires are hidden and the firewall is smooth as a baby's hind end! LOL
