A big problem will be the PCM will not accept the ATX tranny.
The MTX & ATX PCM's are programmed differently.
You are better off sticking with your original PCM and having a custom chip made to accomodate the new engine changes. (timing, compression, cams, fuel, etc)
You will of course need the ST200 MAF and fuel injection system.
The ATX will handle the HP. Though you will most definitely want an auxillary trans cooler. (a must have!) You are getting into the realm of needing more tranny work here... (more line pressure, better clutches, etc)
The limit of the ATX input shaft is ~200 TQ
