I have a 66 fairlane that was a non ac car. I was wanting to put factory ac in the car and was wondering if the duct work out of a 67 fairlane will work I know the 67 had 3 pipes coming out of the heater core and the non ac car had 2 and was wondering if this is a big problem or not. thank you

If you have all the parts, then, no, it is not going to pose any issues. The differences between the '66 and '67 are very minor throughout the car. The only thing you may encounter is if you have a console, the air and non-air cars use different console bases to account for the discharge duct at the transmission tunnel. The air car console is truncated to accommodate the duct.