I removed the heater plenum (under dash)on my '67 VC. I want to clean it up and repaint.
It appears to be a dark gray, is there a designated color for that?

 

Is it AC or non? I’m not an expert on 67 as I have more experience with 70-71. What you are describing sounds like an AC box and that is a resin material that in 70-72 anyway has asbestos fibers in it. You can see the small white fibers in the resin and those are asbestos fibers. The part under the hood that holds the evaporator is the same material. I would just clean them and give them some coats of satin clear. Do the insides too so it can seal in the asbestos fibers forever. Whatever you do don’t sand the material. You can make the fibers airborne and not even know it. The smallest asbestos fibers are invisible and are the most dangerous. The most aggressive I would get in cleaning those parts is with the finest scotch bright pads. I actually took some of the pieces from a damaged AC box and took them to a certified lab. The lab confirmed they are made out of a resin with Chrysotile Asbestos. There may be some fiberglass in it as well. I am a retired Licensed asbestos inspector in multiple states with 35 years of experience. Don’t Put your or your families lives at risk. Clean gently and paint with satin clear. Show some pictures of what you have.

 

Mine is a non- A/C. On the '67, The Heater box/ plenum under dash is all metal. I removed it to replace the decaying sound deadener(padding) on firewall.
That was definitely face mask material. But getting back to the box, it's probably not a big topic but I was curious if there was an original paint color to go with?
I could just go with a satin black. Thank you for your concern.

 

At least on 70-72 cars the steel under dash heater plenum is flat black. I gave taken out several, seen at swap meets and I have two in storage. All Flat black. Not a hint of shine. But again that’s 71/72. Logic tells me yours is flat as well. Are you going to change heater core as well?

 

Also for a fire wall pad check with Ames Pontiac. Not sure if they have 67 but worth a look. They sell two types. The Die cut or molded. The Molded is far superior. It’s more expensive but the aggravation it saves is well worth it. Only difference from original is jute on back is blue not red. I tried the cheaper die cut and sucks. Get the molded

 

 

I think the heater case is more of a flat black. Here are some before
And after photos of my heater case. Maybe the old faded paint appears to look gray.

 

Those moulded firewall pads from Ames look nice.

 

Yes they are the only ones I use. Plastic pegs are usually very tight. You may need to oversize holes in firewall., Don’t go overboard. Looking at your heater box it is the same flat black I see on all 70-72 non AC.