Right guys...another week-or-so and I'm no further on! I have collected the 583 barrels and pistons and one of them, the front one I believe, is, indeed quite badly scored. I have heard that some people say you can re-bore and/or re-nikkasil plate them, but that's as far as I've got. In any case, I would need to order a new piston which the newly re-plated barrel would then be re-matched to.
  C'mon guys, throw me a lifeline! 
 Andy #99  

 .