[Super73]

But.... And this is a big but... If you are going to try and get performance out of the 4.8 or 5.3, your gas mileage is going to suffer a greater percentage than a 6.0. Soon as you put a cam in the 4.8 or 5.3 the volentric efficiancy and TQ down low changes dramatically.

Lets put this on the table, my wifes AWD Trailblazer SS would get 15.5mpg on a long freeway trip when we first got it. With nothing other than a K&N Filter, E-fans and some tuning, it now knocks down 18.8 on a long flat freeway cruise at 75mph with the factory 4.10's.