I have a 1964 series 75 limo with a/c and heater. I am look for a vacuum diagram. I have the 1959,1960 and the 1964 maintenance books but the diagrams don't match up with my system.
Thank you for your help
Vacuum Illustration for the 1964 75 Series is in the 1964 Cadillac Shop Manual on page 13-22, and can be seen in illustration 13-18. I am not sure what "maintenance books" you are using but the shop manual is going to be the main reference book for for these cars. You can almost always find originals, reprints and digital copies online.
We also have some of the vacuum schematics on our Vacuum Schematics and Pictures help page. In fact the 75 series AC/Heat vacuum schematic is the 2nd picture in that photo album.