Oh, and back on the heater box stuff...the earlier Valiants had a different style. The VH/J/K had the blower motor poking through the firewall, the earlier ones had a version with the motor under the dash.
When they came out with the six-pack Aussie VH Chargers, The rear carb would have been too close to the standard VH blower motor, so they made a block off plate for the firewall and used an earlier model heater box.

My old Charger had a factory block off plate on it actually, but I just no heater at all. (I had to make mounts for it, since it normally used the mounting studs from the heater box going through the firewall.)