If the boat were mine, I would probably call it a 6.0 original with a replacement mast. I am not sure if they could hit you for .995 for the taller mast. The rules for the 6.0 were pretty open. There was a version called the Prosail 20. I am pretty sure I saw a Prosail 20 with a double diamond mast. I would look at the rules for the 6.0 original and the Prosail 20.

If I remember correctly, the sailmaker for the original 6.0 was open. So, a first rate set of 6.0 racing sails would not carry any penalty. You might ask EP what they think.

My experiments showed the original jib pointed higher than the big jib on the 6.0na. Since we rarely run a B mark anymore, the speed on a reach doesn't help in a race.

Enjoy your boat. It's unique and a bit of history