What are the hp/ torque limits on the Getrag F35 tranny?

What kind of things could I do to the tranny to increase hp/ torque capacity?

and

Are all 2005-2006 cobalt ss/sc quaife differential equipped or is it an option?

the transmission should be good till 350-400 or more it is the clutch and drive shafts you need to worry about and, how you drive it. if you are dumping the clutch at 6,000 rpm or launching right, that has a lot to do with the life of the transmission. i would do a flywheel and drive shafts if you are planning on going crazy. other wise if you drive right it will hold up. but that clutch is junk my friend with ss have killed theirs at 10,000 miles by racing wrx's and evo's. witch is funny to watch. but treat it right and do the mounts too cause you will get better power to the ground due to less flex. good luck

This will answer your questions.

Europe F35

Type: transverse front wheel drive, five speed manual transaxle.

Engine Range: 2.0L
Max Gearbox Torque: 258 lb.-ft.

Weight: 99 lbs.

Applications: Chevrolet Cobalt SS

Info comes from here http://www.gminsidenews.com/index.php?page=trans_guide

The only thing you could do to increase strenght would be to have the internals treated and hope for the best. Also a capable clutch would make things a little better on the inside too