getting another diesel been out of the loop

well i sold my 250 about 4 years ago now and i've decided it's time to get back into another one...i was pretty familiar with the 6.0 and built that motor from the ground up...this go around i'm not looking to dive in so far..just plan on doing deletes, intake/exhaust and a tuner....my question is which motor should i go with the 6.4 or 6.7...want power not looking for a race truck...advice on motor and also what mods it needs would be appreciated