Same sized wheels' hub caps should fit same sized wheels on Chevrolet (and, most likely GMC) trucks between 47-55. 16" six-bolt car and truck wheels should be the same. Car rims changed to 5-bolt pattern sometime between 47-55 - someone else will have to tell you if hub caps work
Also, my 15" 1954 1/2 ton rims use the same hub cap as I use on my 16" 1954 rims (I would guess that would be the case for all 15" and 16" 1/2 ton truck wheels and hub caps between 47-55).
The bizarre trim ring is a commonly available (non GM) stainless steel "beauty ring" available from many reproduction parts vendors.
