Worn out hubs needing oversized wheeel studs

[jpep44]

While servicing the rear brakes on my recently purchased 1971 F350 i've realized the hubs are not holding the wheel studs. a 610-228 is a direct stock replacement (with a .630 knurl) but not working... anyone know of a stud that has the same dimensions and specs as the 610-228 but with a knurl size of .640 or similar? I've even looked into replacing the hubs but I am coming up empty... ANY help would be greatly appreciated!