The dash controller , and firewall changed in 1973 on the AC cars. Not sure if it remained the same on non A/C cars after 72.
Classic air kit adds a micro switch to the hot/cold slider on non A/C controls. When you move it to full cold, it kicks the compressor on. Kit is designed for a direct bolt in for the 67-72 firewall as well.
If non A/C heat/cold control changed in 73, as well as firewall, it wont be a direct fit. That doesnt mean you cannot make it work, you probably can, but would have to mod to suit.
