I have an 8 3/4 with a 3.23 posi, it is a 489 case. I have a 4.10 to put in it and i bought a ring and pinion install kit. And since i had it apart i figured i should get the posi rebuilt. When i looked in the mancini book it said thick or thin shims. Which one should i get? Also in mancini i saw a solid crush sleeve for the pinion. The kit i got looks like it might already be partially crushed. Is the the solid sleeve better? Thanks for any info.