I have a gmc and it must have the custom heater because the heater gets fresh air from the vents. the cab is still all rusted out though, lol. that looks pretty cool with the filled in vents and the shaved firewall seam. I am thinking of replacing my entire firewall with 16 ga because i will have to change the bump for the engine anyway. I'll probably carry it down onto the floor because it looks like a fred flintsone mobile right now, all holes.
one day i will figure out how to post pics in a build thread, I'm a little computer illiterate.