As you may have read in my other post, i now have my donor car for the mods I am doing on my '74.  The donor car is a '83 Trans Am.
  I have owned 2 of those before, and I recall the ice cold air that they have.  I also know that the air in my Vette is cool, not near cold enough.   The donor car has its A/C in great shape, so i was thinking...
   Since i am doing all this project work on the Vette, and i have all the parts for free anyways, would it work to switch some/ most of the parts off the T/A, would I have the ice cold air that i am looking for?  What parts are they that make the A/C colder anyways?  Thanks! dave.

I thing most of the problem with the C3 is the air leaks in the duct work and the right vent not sealed or working.

Just my 2 cents.  I would install an aftermarket A/C and heating system that is ready for R-134.  Hot Rod Air makes a great retro fit system.  I just finished installing it in the 69 during the restification.  The kit comes with everything.  A Sanden compressor, polished or raw. The evaporator is under the dash along with the heater core so you eliminate the evap box in the engine compartment.  The brackets are Alan Grove and come in raw steel.  I test fitted them and then sent them to the powder coater. You do have to remove both sides of the dash to adapt the duct hoses on a non air car (mine). If you have an air car it is an easier install.  They even have the controls adapted to the console control wheels.  Neat kit.