A friend of mine just bought a set of 4.56 yukons through RR,he's trying to get them installed but the pinion flange will not fit.The pinion is to big to accept the flange.Randys r&p told him that he has a canadian model that requires a different size flange.Is this something new most of us run olders sammys but his is a 94 model.
A possible option would be to pick up some old style flanges and use them. Then you could use a dual pattern driveshaft spacer like the ones we make. Bolt the new style pattern to the driveshaft, and the old style pattern to the pinion flange. The mounting holes would be clocked at 45* to each other, but it should work out fine.