Here are the louvers as done on the 2.9 Alfa Romeo coupe by Touring of Milan as referenced -- that stretched into the cowl itself. (my restoration pictures) Not at nice as what you did above but restoration is different from new fabrication.
[louver panel as cut into the cowl panel itself -- rivet and trim ring attached the panel]
[Front the outside -- riveted and trim ring detail. Louvers haven't been fixed yet]
[From the inside of the louvered hood itself]
Remember this was Touring of Milan coachbuilding methods from the early / mid-1930's era. Each was originally drilled, cut and handformed. I'm sure they would have loved to have had a Pullmax!