I may be crazy,but I am hoping a 460 will give me better mileage than the 400 I have now.My truck has 4.10 gears,C6,pretty much stock other than a rebuild & torque cam about 70k miles back.Mileage is usually around7-8,loaded or empty. I think a 460 won't work as hard therefore a little better mileage. I have a 460 from a 77 1/2 ton 2wd that I plan to put in mine after a little work,hoping its as easy as folks say.