Thanks, yes mine is an April, 27, '67 built Jersey car, with A/C. There is the usual two ports on the vacuum can on the passenger side fender well near the firewall. I am now thinking the previous owner may have hooked the tilt-away to that can, and that the vacuum for the A/C, heat, etc. maybe be plugged off or weakened perhaps. Still checking on it, but the defroster doesn't seem to open, so I am suspicious.
OK, after reading through the last thread, my S code April 27, '67 build, with A/C, has the round cans, and both are mounted through the apron, so that the can is on the back side of the engine compartment. The one under the battery tray has one port (looks to be brass?) and has a "T" on the vacuum line coming in from the manifold, with a downstream check valve on the end going into the firewall (tilt?), and the other has two ports, both have the same diameter.