The 8.5 is easier and cheaper to find parts for and there are many more options as far as gear ratios and aftermarket parts for it. The 8.5 may not fit in your car if you have a '72 or earlier Chevelle.
The Olds rear end is a good rear end and also has a 8.5 ring gear, but parts and options are limited. The Olds rear end has no C clips, if that is important to you. I have found new posi units for the Olds. They are about equal as far as strength in stock form.
'69 RS/SS396 Pro Street
427 4 speed 9"
High Performance Drivetrain Parts & Service www.lubedealer.com/biggearhead
[This message has been edited by big gear head (edited 01-20-2002).]
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