09+ Challenger TR-6060 six speed mate to 03-08 5.7?

I'm doing something similar with the same year transmission in my Dakota, but I have been stuck on the driveshaft issue. Did you have this adapter specially built for you, or is this something that is on the market and can be purchased? Nice work!
I would think any quality driveshaft shop can fix you up... look for a business that deals with heavy trucks as they deal with custom projects everyday.
http://azdriveshaft.com