With the price of gas these days every pound of weight you add you have to drag along with you. Gen3 engines are 4.8, 5.3, 6.0 cast iron Vortecs and 5.7 LS1 and LS6 and the 6.0 LS2 aluminum engines. Now we have the Gen4 engines with the displacement on demand option. I don't know how the Gen4 engine will fare in the aftermarket transplant world.