[R1Ecko]

Any help would be appreciated, especially from experienced tuners or Xanthos, Camarospike. My buddy has an RX7 with an LS5 conversion (who knows why) and he said it's pushing 407 hp. Not sure if that number is wheel or crank. Question is, will headers, exhaust, intake and tune be enough to offset the weight difference or is there something else I should consider, short of a supercharger, that would even it up a bit? I'd like to shed the backseat and any other weight as well.
Thanks for any help guys. I have a little over a year to build so if anyone knows of parts coming down the line those will be considered also.