The Stovebolt Site Forums The Shop Area Interiors AD Windshield Interior Trim Center Pieces

Have you looked under the windshield trim that has the holes in the very center below the center trim piece? I'm assuming that there's a hole in the dash for a sheet metal oval head style screw like the surrounding trim uses. It may seem too long because point of the screw is missing the hole in the dash.Try loosening the perimeter trim screws near the center. That may let you get the screw into the dash hole. The two perimeter trim halves look like they might not be correctly aligned.
You wouldn't be able to use the later 48-55.1 style without some modifications of the trim as they go underneath the center trim piece and over the perimeter trim. It looks like your center trim piece extends behind the perimeter trim.