most dev's make roms for the main carriers. you just need to read the rom information & verify its compatible with alltell/vzw. also 6.5 is the least of your concerns unless you are only interested in the "titanium" interface which is what microsoft gave us in 6.5
otherwise you need to know if you want Titanium, Sense 2.1 or Sense 2.5 as these are the most used interfaces for our device at this time. research what interface would suit you best & go from there. the best way to find out what rom is best for you is to try a few of them out. i might recommend the following
SKI ROM
ROOT ROM
or possibly Energy Rom
after all the only way to know whats best for you is, FTFO
(flash to find out
)