I installed a rebuilt fresh air heater in my '49 half ton. Everything is working well. As you know, the heater motor penetrates through the firewall and is visible from inside the engine compartment. My question... is there supposed to be a doughnut-shaped gasket or a housing of some sort that fits around the motor from the engine side? What is it made of and what does it look like. Where can I find one? I don't believe I've seen such a thing for sale by vendors or e-Bay. The motor is not centered in the firewall hole, and it looks a bit funny from the engine side. Thanks.