You need the radio as well.
http://forum.xda-developers.com/showthread.php?t=1115714 - radio, newest leak
http://forum.xda-developers.com/showthread.php?t=1087617 - dbamf 2
Just read the threads there.. tons and tons of info. Im still testing the froyo stuff for some devs there, havent jumped ship to GB yet myself. As Chris said though, be careful with flashing the radios floating around, you could brick the phone for sure. Just read the threads of the ROMs you want to try and definitely be certain to make sure you flash the correct radio. if you stick to a 2.0 release of something or a rom stated as GB youll be fine with the newest GB radios.