The 5.7 is significantly lighter than a small block not to mention a big block. Secondly you can easily run a 904 instead of the 727 and lose even more weight and put more of your HP to the wheels. Probably be about as fast as a mild big block and handle WAAAAAAAAY better and get better MPG(don't know how much you drive I am just mentioning it).

Your car will be close to 1000 lbs lighter than a challenger witch by the way can run very low 13s bone stock, you would be makeing more HP to boot.