7 1/4 width question....after searching

Looking at what 7 1/4 rears would fit in my valiant that are the same width...
So 64-72 are the same width (53” and change)

73 and later 7 1/4’s are slightly narrower? (51” and change)
Am I correct?
And all are small bolt pattern?
73 and up, can be BBP if they came from a disc brake car. I don't know about the width difference.