['ol Pinion head]

231127 was the original part number for the '71-87 8.5 posi clutches.. These were discoed by GM near 20 years ago & around $112 a pkg. Through the 90's, I normally bought em 8-10 boxes at a time @ $49- 60 a box. A Buick guy had the clutches reproduced in the mid 00's, they dont have the same swirl pattern, but they work fine. To properly shim up the side gear to spider clearance it takes having a good assortment of clutch shims. GM discoed the clutch shims for this style carrier even earlier, early 90's, so most guys didnt have a selection. One thing I've done is take a pair of used 8.5 clutches with the ears on them. Cut the ears off with the Dremel tool, then use these non splined clutches as the base of the stack to add a thin service or aftermarket clutch shim to. The OEM S spring carrier clutch shims will measure from .088 to .102 thick. The two of them are typically very close to each other in thickness. At the very least, you want to replace with the shims that came in the carrier. More often than not with original side gears & spiders, it will take being a .001 to .003 thicker on each side to tighten up the tolerance. The spider gears in these are larger than the small brittle spider gears that were used in original GM 12 bolt "chevy" posi carriers. Just one of the advantages over an original Chevy 12 bolt. With original 12 bolts the vast majority of them do not have much cast steel under the cap mating area, this is a weak area. So are the thin stock 12 bolt caps.