Sure you can get 20+ with a slant or even a small block if you used an overdrive trans but get any old engine to make 475+hp like the new HEMI's and still get 25 mpg. Or make 700+ hp and get 22 mpg highway. I agree with you, overall classics are way cooler than new cars. That said, my long term plan for my Duster will include a 6.1 or 6.4 HEMI and a 6 speed or OD automatic