I just saw your thread on wildguzzi.com, so Duh! to my previous post. Those guys had already said everything.
Too bad about your tank. I hope you are able to find a replacement reasonably easily and for a decent price. I'm currently fighting with the petcocks on my 74 Police. Someone seems to have welded on 1/2 stubs, so the new petcocks I bought from MgCycle don't fit (12mm). Time for a work-around.
But as I said before - well worth the effort. And you have the disk brake too.