you don't design a engine around a rod ratio.... you build the right piston and then put a rod into it.. your wasting your time worrying about the differents between the 6-5.7. i would put you worry were it belongs the piston.. if it worrys you that much off set the wrist pins with custom ones. but i can tell you from 1000s of hrs on the pump it doesn't do chit for power or how durable it is...