I have rebuilt the heater/AC unit on my 67. Is there a grommet or seal that goes around the tubes passing through the firewall? I am having trouble finding this part in parts catalogs. When I removed the unit, there was some kind of rubber all over the tubes and sealing the hole through the firewall. What could this be?

 

I would like to know also. I have aftermarket a/c and there is no seal around those hoses coming thru the firewall and I believe that is the reason I smell like exhaust sometimes

 

this is all i could find at mustangdepot,that black stuff must be something a previous owner made.