tried searching, but no luck. I think I can get a complete 12 for 2500, I'm kinda lost on this. going to need to hold 500 hp and a 3300 lb car.

 

A 12 bolt will stand up to 500 hp easy and a 9" will stand up to 500+ hp stock
moser and currie make direct bolt in for an F-body
Randy

 

Both are equally strong. Both can be upgraded to be stronger although the 9" can be upgraded far more than the 12 bolt. Both have their advantages and disadvantages.

It becomes a personal preference. What do you want under the car? Neither will be a bad choice.

I run a 9" under my car.

 

I like the 9 inch personally. Your gonna shell out a bunch for both, so I'd suggest looking on ebay for a 9 inch since they have great deals on em there.

 

I run a 9". It was custom made for my car. Cost about 3000.00. I run Moser 31 spline axles with a Moser full spool and Richmond 4.11 gears.

 

12 bolt rears are a little more efficient than a 9in., but the 9in is stronger. Either one is plenty strong enough for 500HP and a lot more, especially when you go with an aftermarket unit like Moser, Curry, Strange ect.