I have my non-B visa in my old passport, together with my last exit stamp and re-entry permit. I have the latest entry stamp in my new passport. I'm planning to do the 90 day report by post, but what photocopies should I enclose? I'm planning to just post back the usual bundle together with a photocopy of the main page of my new passport and the latest entry stamp.

You need to go immigration and get your stamps transferred. I don't think they will accept your 90 day report until you do it.