Sounds like an energetic project. Keep us posted with progress pics & notes on this. As far as a piston goes, check with JE or Mahle.
A few years back, I remember MHR & Mat Shearer both talking about filling & machining the cases to accept a Puma or Sabertooth  cylinder. But I never heard anything more about them. Maybe the builder can look into this?

Do you by chance have a link to CP Cylinder Swap MHR and Matt Shearer did? Did you ever see any pictures of the transplant completed or hear how it ran?

I would LOVE to check that out!

Thanks man,