I personally set my limit around 350-375 with PMR's. I think yeah 'you can throw some hybrids in it and get there' or NOS, or Pane, but I don't know how safe these things are. My goals are a well-tuned, driveable and smooth 350-375hp, not just slobberin enough fuel through it to eliminate the mosquito population for six counties.
I might also add the 350 with Big Oil, and 350 without should feel a whole lot different, because Big Oil helps the truck pull all the way through the powerband, where as without it, you may peak high but fall off. So Big Oil greatly adds to the useable power.
With the proper programming, I think Big Oil and PMR's can live together, keep it efficient power, tuned well, and keep CP's low, and you have it. Jody Tipton knows how to program for this. ...and yes, you'll scare 400 to death.