I'd listen to these guys IMO, they wouldn't tell you wrong. I've learned a lot from these guys.

 

on a 4.8 id go with a 70 mm a touch smaller but not much would work also

 

You have to remember that if you start with this turbo, you more than likely will have to cut up some of your hot side pipes to make any other turbo work. Bottom line, don't put it on your truck, you will be taking it back off right away for something like a 70mm.