The t-56 that came in the 03 - 04 cobras are rated for 440ft lbs. The Viper Spec t-56 is rated for 650 ft lbs. So really you would only be gaining 50 ft lbs going with the viper t-56. I put in the Viper Spec this year, and the great thing about it is the .5 ratio final gear. I can cruise the highway at 75, and hardly spin 2000 rpm. I swaped from an auto to the T-56, and I needed the tranny, a new bellhousing, 26 tooth clutch disk, New crossmember, shorter driveshaft, and modify the wiring harness. There is other stuff I can't think of right now, but I got everything I needed for the swap (minus the clutch and flywheel) from D&D Performance. They were very helpful and knowledgeable. They list their kits, prices, and parts at
http://www.ddperformance.com/