If using SPR and already rooted, why not just download ROM manager from the market, and install BB v.01 from ROM manager. Just make a backup to SPR before doing anything. When you flash the new ROM make sure your wiping data and cache.
Oh one other thing. For some reason after flashing ROM manager Ive noticed that when you go to flash the new ROM sometimes it will reboot the phone and freeze with the Motorola symbol. Just drop your batter. Reboot. Flash ROM manager again,(will take a second this time) . Now you should be good to flash 2.2