The file named *FitMewtwo00 PSA* is the Mewtwo PSA compatible model file, this means that you can add this model to any other recolor of this Brawl Mewtwo. 

Once you have your custom texture done, and if you want it to be compatible with Mewtwo PSA, just open the .pac file = ModelData[0].BRES = FitMewtwo00.MDLO, now right click and replace it with this file, now your texture is fully compatible with my Mewtwo PSA.

Enjoy!