I already responded to your post on the CrossFit forum, but I guess here I'm more free to go against the CF methodology without reprisal.
Anyway, is that your only goal? Just to be a runner? There's nothing wrong with that, but if that's what you really want, then the key is basically to do as much running as possible without hurting yourself or your recovery.
Here's a pretty good 100 mile training program:
http://www.hillcountrytrailrunners.c...Plan_mike.html