Install EvolutionX dashboard on your Xbox as an application - you don't need to change your primary dash.
Create a directory called BIOS under your Evox dash directory (it may already be there). Put iND-BIOS.5003.67 in the directory you just created. Make sure that your evox.ini has the line:
Item "Flash BIOS",ID_Flash_Bios
in the menu section.
Run EvolutionX. Select Flash BIOS from the menu, scroll down to your bios, and flash!