Is this 496 a special build or a 8.1L Vortec V8?
If it's the 8.1, we agree that it is an awesome engine...have it in our Workhorse W24 (Allison 6speed and Meritor rearend) equipped motorhome. I understand that engine was also put in the Kodiak/Top Kick medium duty truck.
It must be a kick to drive the Yukon with no TT hooked-up.
Our average mileage over the years of use is about 8-8.2MPG...not bad with a 37' Class A towing a SUV
Safe travels