Depends on what you mean by flange width, but the key is the backspace on rim.
I know a fella that has a '67 B body housing in a '69 Valiant. This rear reportedly measures 59.5" between the drum faces. He says '94-'04 Mustang rims fit (8" rim, 5.7" back space, 275/45/17 tire).
In my '69...