Another suggestion....Camaro IROC-z's (89 for sure) run a posi/disc in 3.08 and 3.42,5 lug, 4-3/4" pattern, 62" wide from backing plate to backing plate. The 3.08 goes behind 305 T5 combos so it's no wimp! I have non-power discs which work great! Replacement brake parts and seals are expensive but less than bolt-on conversions. I found the later model ABS diffs were very dear. Hope this helps.
