My guess is that the panel-truck RPO deluxe equipment stainless steel fender moldings (bars(12)/spears(2)) are being referred to.
http://1954advance-design.com/Documents/EngineeringFeatures/Page93.jpgI do not think that any Advance-Design trucks had any GM chrome options/accessories on the fenders, except maybe the stock/standard hood front and side emblems (chromed in some years).
Restoration Specialties, Inc. sells clips for many applications. I obtained exact-matching clips for the panel-truck rear window stainless surround trim.
The problem is, you'd have to have an original-style clip in order for them to match up a part. Or, look at their catalog (illustrations are to scale and dimensions are often shown) and buy a few that look like they will do the job.
Maybe someone who has installed the fender trim will post information on the attachment clips.