The back surface of the "vacuum pot" is not flat on your unit. The back surface of the original pot and the back of the unit in the Classic Parts photo is not the same as on your unit. I have bought two units from Classic Parts and they look like the photo in your catalog, not like the unit your received. I think they sent you the wrong unit.
The collar from a car is different from the collar from a truck but either one will work with the right unit (as long as you bend the vacuum line).
