[ShadowSky]

The only Real enemy to IRS is wheel hope and axle strength.

Gm 12s are not bad if they are built right, and pinion depth and lash is set correctly. I have saw 10 bolts make it to the 9s!
Sadly i was not one of them, the fasted i was able to get a 10 bolt to was 11.0s.

9'' are the bad boys on the block, cause that have 3 teeth in constant connection where others have 2. The street guy hardly races his car a 9 might be over kill cause of the gearing robs you of rwhp. For a hard core guy or a guy going with the plan of adding gobs of hp, it a insurance that you have a damn near bulletproof rear end..