The 865 engine has different camshafts. The 790's cam breathes better at top end. I'm not sure if the ignition timing was altered as well, but I'm sure one of us can answer that one.

The 904 kit with 790 cams seems to be the best bet overall.

Steelheart- '03 Speedmaster Black/Yellow The Hayabusa Killa 16" Shorties/140 mains/Airbox drilled Procom CDI "There is no cure for Celibacy. But we can treat the symptoms."