No doubt in my mind you will gain 1-3 MPG running empty with a GV.
Your engine should handle it easily. My 7.3 (dynoed at 230 HP/560 ft-lb torque) handles it easily even with my super long legged gearing. Your 6.7 should sneer at the load.
What i would suggest that your have a talk with your favorite automatic transmission guy. I use the GV fearlessly because I have the stick. Slowing the engine down at a given road speed reduces the flow of ATF to the cooler, allowing heat to build up in an automatic tranny. Excessive heat makes for spectacular (parts scattered down the road) and expensive transmission failures.
If you think your transmission will take it, I say go for it - particularly if you drive the truck a lot.
Your engine should handle it easily. My 7.3 (dynoed at 230 HP/560 ft-lb torque) handles it easily even with my super long legged gearing. Your 6.7 should sneer at the load.
What i would suggest that your have a talk with your favorite automatic transmission guy. I use the GV fearlessly because I have the stick. Slowing the engine down at a given road speed reduces the flow of ATF to the cooler, allowing heat to build up in an automatic tranny. Excessive heat makes for spectacular (parts scattered down the road) and expensive transmission failures.
If you think your transmission will take it, I say go for it - particularly if you drive the truck a lot.
