Not sure if it falls under this category. But thinking of useing this rubber seal to seal ac delete box to the firewall. What you guys think? Worried about heat specifically .
https://a.co/d/4L30UgP

There’s a seller on eBay that has the proper gasket for the heater box. Search “camaro heater box gasket”. It’s like $70 with shipping though.

Homemade gasket, Post #1171, https://www.thirdgen.org/forums/ltx-...ml#post6293557

Personally I would use butyl tape, specifically 3M windo-weld ribbon sealer.

I used some 3M strip caulking. Works like a champ and has held up for over a decade.

Factory used a diecut, closed cell adhesive backed foam

Here's the box I'm working with. It's not the cheap one for vehicles that weren't originally equipped with ac. I got the one from hawks/acdelete.com. it's actually fiberglass and has a lip that mates to the firewall and isn't flat all.the way around

You got your thinking backwards. The stock metal housing is better.... as you'll find out when you try to install that fiberglass piece.