Finally got around to building the inner firewall on the Austin. It's just had foil backed sound deadener on it all summer, and looked pretty tacky. I made cardboard templates to fit around everything, and then traced them to some 1/4" finished plywood. After cutting them out with the jigsaw I covere them with carpetting, and installed magnetic latches on the back. Then matching strikes on the firewall with clips to set the interior panels off about 1.5" from the firewall. Should also help insulate from heat and sound too.
I made them in 3 pieces so I can remove them easily for maintenance, or to run any further wiring I need behind them.
This winter I'll pull the seats back out and with the rest of the carpet remnant I bought, I'll cover the wool felt and sound deadener I have on the floors.