Screwed on plates is correct for 1947-1950 trucks they do not attach with rivets until 1951 onward.
Ok in owning 25 trucks Chevrolet and GMC this is what I have come across:

Phillips screws 1949-50 only, it seems a unique screw always the same NF with a flat point 3-4 trucks my own included (purchased from original owner).
http://community.webshots.com/photo/2917615890102454676KACyfz

Clutch head type unique though becasue they have a head like a bolt 8-9 trucks 47-early 49 usually.
http://community.webshots.com/photo/2612842870102454676nYHeFa
http://community.webshots.com/photo/2493107830102454676JMVBEB

Rivets always on the 1951-55 1st Series 11-12 trucks. Notice the 53 plate with extra numbers.
http://community.webshots.com/photo/2074469990102454676dIwcIS
http://community.webshots.com/photo/2344936220102454676Nqmtbj

I am curious what others may have found.

Last edited by Brad Allen; 02/17/2011 5:42 PM.