Going back several years, we've published stories about using the highly available Holset HX35 and 40 turbochargers on the 6.5L diesel. The common 35 is sourced from a 1994-98 Dodge Cummins (and other apps). It's wastegated and there is a Turbomaster available for it. The 35 works great on stock compression engines and the 40 works great on 18:1 engines.
Going back 10 years now to 2008, here is a link to a story we published about using the Holset HX35 on the 6.5L diesel:
http://www.thedieselpage.com/members...rysholsetc.htm
I tried and tried - going back more than 10 years - to get some vendor somewhere to offer a turbocharger option that performed better than the stock GM series. My pushing, pleading and cajoling never resulted in a turbo kit being offered. We've waited too damn long, so I began the process of designing one in 2017. Later this summer, I'll offer a sweet looking bolt-on kit that makes swapping a Holset HX35 onto a 6.5 both easy and inexpensive.