Well as some of you guys may know im a big chevy fan and my family has all GM products. well im going to buy my grandpa 72 chevy that he bought brand new in 1972. it has a 400 small block farily clean except he used to live in nebraska so it has some rust that will need to be fixed but otyher wise farily clean.it will get completley re-done. my question is do you guys think if i put a a 5.3 or 6.0 vortex engine in it will it get better gas milage?? casue your still pushing around a brick? pics will come