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.
You won't be putting 3.54's on a 4 series case. There is a 3 & 4 series gear that I know of in 4.10's. Nothing 3.73 or 3.54, you'll need a 3 series case. The spacer is to put 4 series gears on a 3 series carrier.
Take the cover off and see if there is a spacer on your carrier. If so, you have a 3 series carrier that you need.
