Ez,
The trigger(s) will be about 2" behind the end of the barrel, so add that for sure. And beware of checking on the ends of your blank that you might like to trim away. Then, depending on how the blank is shaped, you may have to shift your pattern around some to get the best fit, grain flow thru the wrist, etc. How long? I'm thinking 68" minimum, but the longer the better!
-Ron