It's a 95% chance that this 10 bolt is an 8.2" Very few Chevelles got an 8.5". You would need to pull the cover off to meaure the ring gear diameter to see which is it. $200 is a bit high for a 10 bolt. I see those rears for $100 max all over the place. You will spend about $850 rebuilding it if you cannot do it yourself. An 8.2" 10 bolt will not hold up to a stout big block. It will, however, take the abuse of a mildly built small block without a problem.
Tom
