There should be 2 screws and a row of nails that are hidden by the top tack strip. However if the panel underneath is missing then some things may have been altered from original by a previous owner. Parts for high production models like coupes are not hard to find on ebay or Fordbarn. This vendor has that panel for sale. https://www.ebay.com/str/goodjunkrod?_trksid=p2047675.m3561.l2563
If its like my late 31 Tudor, the header panel cover went on after my sun visor, after I put new top wood and header in. Wait before tearing it apart, get the panel/header cover first. Bratton’s, Synder’s, Bert’s , Mike’s Affordable should have it new.