Hi Mitchell,
There are quite a few differences in the '54 sheet metal.
If you go to Keith Hardy's site
http://chevy.oldcarmanualproject.com/index.htmyou can look up parts in the 1929-1957 Master Parts Catalog. For instance, on this page
http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0628.htmthe rear fenders for 1947-1955 first are listed as part #3700271 (left) and #3700272(right) so they all the same. By the way I don't know what the note (exc. SGL.UNIT) means.
The front fenders of the '54 are very different from the early ones. They have a recess where the parking lites go. The inner fenders are close (though not perfect). I put some early inner fenders on my '55 first with pretty good success. The cab is of course quite different (with the one piece windshield) and the bed and tailgate are different between '47-'53 and '54-'55 first.
Let us know how it goes and best of luck to you.