Both of my 51 Big truck cabs (1-1/2 ton) have the above shown rivets.
My 48 has clutch head screws.
This page has the correct door post plates for the year a guy has and the correct rivets and the rivets aren't expensive compared to some sites
http://www.classicparts.com/Paint-De...oducts/848/2/0. I just received a door post plate for the 48 and it's a nice unit as mine is mangled and painted over but I will keep it in the glove box for show and tell if case needs be.