you keep posting LS-X ther is an X in the series.Go with the 5.3 for economy.the LS-3 has enough everything in one package at 430 hp,a hot cam and minor tweeks is 480 hp
like I posted above,its the roller cam/fuel injection and ignition that makes it a nicer package. spending 12 k to save $100,oo worth of fuel is not good math.If you want it all in an old car the the LS line has a lot to offer.
Old engines can accept fuel injection,roller cams and better ignition. The cathedral heads do offer more potential. O/drive transmissions come in many varieties,but at a cost