[clay68c10]

The main case mounting area on the firewall was next. The big opening towards the center line of the truck is the same for AC or heat only. It's the outboard side that's different. I used a beat up case for my mockups but I could have used my refinished one, it isn't harmed or disassembled beyond anything normal when you do this.
Some of the mounting holes line up already and some don't. I didn't take any pics of that part, I got the mounting holes done a couple of years ago.