First unlock your phone with the HSPL found here:
http://forum.ppcgeeks.com/showthread.php?t=84822
Then find a 6.5 ROM you like from the Upgrade Forum
http://forum.ppcgeeks.com/forumdisplay.php?f=102
Take the file (RUU_signed.nbh) and put it in Cfay's custom RUU found here:
http://forum.ppcgeeks.com/showthread.php?t=82321
Then run the ROMUpdateUtility.exe. Done!