Vintage / Old Air mounting and firewall connection?

[OrrieG]

I am getting ready to smooth my firewall. I am going to eventually install a Vintage Air or Old Air Heat Defrost Air system. Vintage Air says they use the stock heater mounting holes. Old Air is not specific. Also they do not show any installed photos of where the heater and ac hose connections route through the fire wall.

I looked at some of the photos here and could not find any photos that show the firewall side of the installation.

Does anyone have any photos or installation info they can share? I do not want to waste time welding and grinding up holes just to redrill them. Also could I weld in studs facing the inside in the heater bolt locations to mount the unit? Thanks Patrick