Vacuum switch problem solved
'64 air coupe; previous post indicated I couldn't get heat when vacuum switch replaced. After getting the third switch that didn't work from LI Corvette, who, by the way, were very cooperative in sending me the 3 switches, I decided to take the switch apart, lube the o-ring, and try again; still had no heat. Took the switch apart again, and enlarged both inlet and outlet ports to 1/16"; that solved the problem.