Hey Webb.
I want to say that the heater box is not included, but that memory is a bit fuzzy so don't take that to the bank.
Regardless, you can get them in either steel or aluminum, so make sure you know what you're getting.
The one I ended up using was the steel triangular one that you can actuate from the cold side so you don't have to punch another hole in the firewall to get a cable out there. I believe I got it from Spruce.