Here's a link to the free generic information packet from the GM Heritage Center archive:
http://www.gmheritagecenter.com/gm-h...tion-kits.html
Find Chevy trucks and click on the one for 1972. This will show you all the generic options and content that were available for the '72 model year. I think it has a representation of what the various hub caps were.
By the way, nice truck. I see you have the same custom gas cap as "the farm truck".
K