A question that has been beaten to death, however I still have something to add. How much power will a moser 12 bolt with a spool and 33sp axles w/ cover actually handle compared to the 9" in similar trim? I am not concerned with the minuscule variance in drivetrain loss. I am looking tin the future to do something radical and do not want to purchase two rears. I am actually looking at the m9 as well. Any reviews yet on this piece?

 

I've run mine at 800 flywheel HP/800 lb-ft with no problems (Eaton HD posi, not a spool) A buddy of mine ran his at 900 flywheel HP with a blown 383 LT1 in a 3,900# convertible. He switched to a 9-inch when he went to 1,125HP and then to 1,350HP.

 

A properly set-up 9" will outlast the same level built-up 12 bolt and once your near 4 digit hp the 12bolt has real issues especially in a heavy car.

 

If you only want to by 1 rear and you have big plans for the future, buy the strongest one you can find... Seems pretty simple.