Why not a 20v head?
aside from aftermarket cams (pricey :P ) it should do as a good base. Lets face it, theyre designed to rev, a good port/polish will clean up the airflow and they are nowhere near as old as a bigport.
that said, the only values that could be wrong is the power. Toqure is a big selling piont on the gze (lol thats why i bought one!) and anything that gains over stock is a bounus. How bout playing with the timing next?