HVAC systems and firewall

[Gearhead1]

I've searched the site but can't find answers to a question. Are the cab firewalls substantially different between those trucks factory equipped with heater only, and those with A/C? I know in the squarebody trucks there is a significant difference on the firewall depending on which way the truck was built. Is the only notable difference in GMT400's the holes for the evaporator lines? Have other forum members done such a swap before, either adding A/C to a cab or else the reverse and eliminating it?

 

[someotherguy]

I've looked at doing it for a customer that bought an ex-AT&T fleet truck not equipped with A/C. It was a Vortec-era truck, like a '98 or '99 classic. From everything I could see, it was simply missing the holes punched in the firewall sheetmetal for the evap lines.

You'll need pretty much everything from an A/C-equipped donor truck, though, including the HVAC ductwork box from the inside of the cab. Dash ductwork, harness, controls, etc. This is probably a far easier swap on 88-94 vs. 95-up as the wiring in the earlier trucks is a bit more modular depending on equipment, and less complicated overall.

Richard