While there is no data to document any numbers or percentages, it’s a safe assumption that fewer convertibles were equipped with air conditioning from the factory than were coupes or 4-doors. People have often asked me why someone would have air conditioning in a convertible. My answer is simply that you can be comfortable no matter what time of day it is or what the outdoor conditions happen to be. If the sun is too direct to tolerate having the top down, you simply put the top up, roll up the windows, and turn on the air.
As is the case with certain options due to body differences, there are two differences between the ’66/7 models’ soft top and hard top a/c systems. One difference is that convertibles have a double cross beam under the toe board, thus need two grommets for the hose that runs under the car from compressor to the drier. The other is the copper pipe where it exits the passenger compartment under the rear seat. On hardtops, it exits almost straight out the corner wall of the floor pan rear seat riser, which goes around the corner in a large radius. In a convertible, there is a floor brace in that location that is in the way, so the pipe for them goes around the corner of the foot-well, along the seat riser wall a short distance, and, using a soldered-on right angle elbow, goes straight through the wall to the hose fitting.
In the pictures I have strapped two pipes together, one is from a hardtop car and one is from a convertible. The convertible pipe had been bent slightly in several places, so I straightened it as best I could. Thus it may not be in exactly perfect shape, though it’s close enough to illustrate its differences. The convertible pipe is missing its grommet.
Note that only the rear end section is different between the two. Here is a close-up.