In answer to the "will there be changes" question. probably. It's unlikely that the first set will be perfect. I'm sure John will run a set and check everything over several times before he releases them for production. That's how he is. I would not be surprised to see him send a set to someone else who will also test them (like Ted or Lonny) before the rest of us get a chance to break them.
John's pretty careful about his parts working. Maybe even a bit of a perfectionist, nothing is just "good enough," it has to be as right as he can make it. Ted's got much the same work ethic which may explain why Y's have been developed as much as they have been in recent years. There were a multitude of issues with the first parts run from the SpeedSmith tooling, and those all had to be addressed. Rocker bosses placed the rocker shafts in the wrong place, the water jacket broke through the casting, Bosses were wrong, ports didn't work as advertised........blah, blah. All of this has to be fixed and verified before production.
Frank/RebopBristol, In ( by Elkhart)