There is a flange you can buy that bolts up to the 3 bolt flange on the cts v t56. You can have youd local driveshaft shop make you a slip driveshaft i believe the yoke is a 1350 so its pretty beefy. Just another way to go about it. I have a complete drivetrain from an 05 CTS V so I've done a little research.

I thought i had seen something like that before on another forum but i couldnt remember. do you know who makes that adapter?

Yes sir its made by The Driveshaft Shop. Heres a link.
http://www.driveshaftshop.com/drives...nger-05-06-gto

Awesome! Thank you!

No problem

also f-body shaft wont work, because of 2 pcs synchro on f-body. gto/cts-v/and corvette use 3 pcs synchro. f-body and gto shafts are the same length tho.

You would need a GTO mainshaft as stated to convert it including tailhousing.

That adapter Ujoint part looks pretty slick