Jim,
Thanks for that link to JCs Technical Article on the side mount spare tire carrier. One of the few valuable improvements to JC's website is that we can now link to his excellent Tech Articles:
http://www.oldchevytrucks.com/Articles/1947-1955.phpI now know what that bedside bracket is for. I think the 54 pickup I am now restoring has that bracket. I might even have the spacer - if I do, I'll post photos.
Thanks,