There's a lot of bogus info out there, as you've discovered. I don't know why it can't be fixed.
I can verify these B housings from ones I've measured personally and still have.

B housing width:
'64 = 55 5/8"
'66-'67= 54 1/4"

I copied/pasted these from this page: http://www.moparts.org/Tech/Archive/axle/16.html but took out '65 because I've never measured one.

The overall width is axle+axle+1.5" and for 4.5" bolt circle overall is about 5" more than the housing width.