I doubt your truck would gain much if anything with the CTS converter. I know my 2017 HD ( same powertrain still as your 08) brake torques to like 2300 or more with the stock stall. Even if it went to 2600 whooptee doo lol.

 

LOL thanks.
Out of a pure luck search I found a Co that can get me a CD converter that I need for almost half price, great service too.