my 1976 small bolt pattern 7.25" measured 57 1/8" drum face to drum face. they want that measurement since that's where the wheels mount and determines axle shaft length and where the wheel sits in the wheelwell. housing flange to housing flange doesn't mean much without knowing what brakes you're using (1.5" wide drums, 2" wide drums, 2.5" wide drums, discs off of a jeep patriot, etc). I was actually quite suprised when I measured my duster that with the stock width, even though it has that hippo on stilts look with the 215/70R14 tires on small bolt pattern ralleys (which measure .5" positive offset, or 3.75" backspace for 5.5" wide wheels), the tires were about perfectly centered in the wheelwell, 2" spacing to the inner wheelwell and 2" spacing to the lip of the wheelwell opening.
so what width you want to do will determine what offset wheels you plan to use and how big of a tire you want to go. 0 offset rims and maximizing tire size, I'd want the width probably 56" or so. +30mm offset (late 90's bullit rims), you'd probably want something more like 58.5" wide....