Hi Jeff,

Here are the two side by side http://www.picturetrail.com/sfx/album/view/23783779 the white is 54 and the brown is the earlier. As Tim pointed out, pretty significant differences. The 54 is shaped differently and tucks under the grill slightly. Also the license plate brackets are different.

Good luck finding the perfect parts this weekend. See if you can find the "dummy" center bolt. It is a steel bolt covered with a thin stainless cap and secured with a spring nut. http://www.oldchevytrucks.com/blog/2010/02/lost-bumper-bolt/