I'll measure and post back in a few minutes.
Edited to add: Okay, here are some measurements from my 1974. I took them from the inside because it is pouring rain outside.
Now, there are trim pieces around the perimeter (and I have seen these vary), so I have just measured the "working window" part. That is, the part of the frame that has the crank handle in it, but not the "trim flange" outer part that is outside of that and overlaps the shell. I think the part I measured would correspond reasonably to the rough opening.
The square-cornered Burdick jalousies that are at the dinette:
The square-cornered but rounded insert Hehr jalousies that are over the stove and in the door (same method of measurement):