i live in the desert, and out here, we keep our CB's out of the sun.
car temps here reach over 150*F in the summer, and the main problem is that the wax that manufacturers put around the VCO and other temp sensitive sections of the radio gets so hot that it melts off the PC board and drips onto the bottom cover.
once the wax is gone, the components that are supposed to be protected from temp variations are now susceptible to them.
remember that when a CB is right side up, the PC board is upside down.
i cant tell you how many times ive had to scrape off the wax from the bottom cover of a radio and re-melt it onto the PC board.
now, as to the severity of the freq drift caused by this, i really cant say because i dont expose my radios to that direct sunlight.
i am surprised that a cadillac doesnt provide a better mounting solution than the top of the dash.
arent they known for being big cars?
i will try to find some pics of that year model and see if i can come up with something.
LC