Yup. I think from 3.54 to 4.10 is one case and 4.56 on up is another. I THINK that's right. Call Cass like DuBob says. That will eliminate any mis info.
spacer ring, most dana 60's I have ever seen with 4.56 and lower gear sets have a spacer between the carrier and the ring gear with longer bolts. Been awhile but when I rebuilt my B body 60 cheapest parts were from jeff's bronco graveyard. Been awhile and don't know how good prices are now.
If you want to run 3.73 you can remove spacer and get standard length ring gear bolts.
Rusty you are correct but that carrier is a rare bird. most of the time a spacer is used.