I've had this never-ending process lately of removing all of the HVAC from my k10 so this weekend's project was to fill in the firewall so it's not so freakin' loud when I drive it.... plus the fumes were a downside. 
Anyways, here's some pics...
Before:
and After:
It's not exactly how I wanted it but it works great. The cab is quieter than when I had all the ducting and the shoebox on the firewall and obviously a heck of a lot quieter than when it was open...
Eventually I'll move the battery and overflow tank up there so I can ditch the inner fender wells but for now this'll work.

Anyways, here's some pics...
Before:
and After:
It's not exactly how I wanted it but it works great. The cab is quieter than when I had all the ducting and the shoebox on the firewall and obviously a heck of a lot quieter than when it was open...
Eventually I'll move the battery and overflow tank up there so I can ditch the inner fender wells but for now this'll work.


