Still use the same chart. It is simply a mechanical change and the nitrous knows nothing about the engine it is entering. So as long as your FPR is 1:1, business as usual except for possible duty cycle issues. How much nitrous are you planning on injecting and what are you injector's duty cycles currently when running 38-42psi? I am also assuming you are running as big as possible fuel pump and lines. A 427 is no joke and coupled with a 175hp dry shot can be one helluva ride. You want more then you will need to up the solenoids, lines and probably the fuel injectors.