The masthead of March 1987 Ron Paul Investment Letter lists "the Hon. Ron Paul" as "Editor and Publisher" and "Llewellyn H. Rockwell Jr." as one of several contributing editors.
An undated personal solicitation letter--signed by Paul--asking the recipient to subscribe to his newsletter in anticipation of (presumably) the 1988 Libertarian Party Presidential nominating convention.
The April 1988 Ron Paul Investment Letter lists Paul as Editor.
The May 1988 Ron Paul Investment Letter lists Lew Rockwell as Editor. It also advertises books by the far-right conspiracy theorist Gary Allen, who was a contributing editor to the Ron Paul Investment Letter.
Let's just add this to the pile along with Ron Lawl´s observation that 10 years ago Paul was not denying authorship of these newsletters.