flashing with another carriers rom?

[cdkg]

I'm interested in flashing my sprint 6700 with Bell Mobility's 3.31 http://www.utstar.com/pcd/downloads/...20AKU3.3.1.zip (sorry new to posting so bear with me on the sloppy link).

I've done this in the past but I can't for the life of me remember how to do this. I have tried a few different things (including reading WideAwake's "how to build a custom rom"). I remember a long time ago flashing with a telus 2.2 rom and all I had to do was delete a few files and drop MaUpgradeUt_noID.exe in with the ruu.dll and stuff.
Any help with this would be much appreciated.

Thanks