71 Mach 1 cowl difference between AC or Non-AC cowl.

I've decided to replace my rusted cowl in a non-AC car. I also have all the AC parts and heater housing from an AC car. There is an aftermarket vendor that makes a repro non-AC cowl assembly. I know the firewall cutout is different between an AC or non AC car. What is the difference between the cowls?

I decided since I have to go into the cowl, I want to do it right. I don't want to go back in 10 years from now.

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Non AC car has cowl vent holes for both the driver and passenger side air vents. AC cars have cowls with only one vent hole. It is easy to convert a non AC cowl to AC by welding a flat piece of sheet metal over the hole. I've not done this but others have on this site.

Contact Don at OMS to get a cowl.

This raises a question from me.

Can OE A/C components be directly retrofitted to a non-AC car, or does the cowl mod HAVE to be done?

If so, what component(s) will not clear the right vent?

I have a complete OE conversion "kit" for my non-AC car, wondering what I'll be up against when the time comes...

I think you'd be money ahead to keep the non - AC box and put in an after market assembly. The new aftermarket AC systems are much better and easier to work on. However, if you proceed I'm going the opposite way from an AC to non AC assembly in my car. You will have to cut a hole in the firewall for the AC lines, change all the duck work in the dash (EVERYTHING including the center dash vents that where not on non AC cars), there are some type of different mounting brakets on the cowl itself, you may be able to keep the driver side vent as a foot air exchange (meaning you may not have to plug it it just will not blow from the dash), and the worst part is making the jungle vine vacuum mess work (this from what I understand is incredibly complicated, others might have other ideas).

Keep in mind with the AC box a simple heater core replacement is a massive undertaking, that is why I'm de-optioning it and then after re-optioning it with aftermarket air.

Hope this sheds some light.


I would say it would be a full but able retrofit from AC to Non AC and back.