AJ, the measurements on a '76 -'78 I know are the same with a maximum ceiling height of 6' 6" and under the A/C covers it's 6' 2 1/2" front and 6' 3 1/2" rear. The floors on these Newell's must slope the same as a bus from front to back. It would also depend I suppose on the type of flooring you may have.
Now, there are shorter A/C covers then the ones I measured. Another option if the A/C cover clearance is a potential issue would be to go with a Newell with basement air.
I know when you get to the newer years you will gain some head room.
Hope this helps.
Ken