The 47-55 Factory Assembly Manual does not show any "anti-squeak" (welting or gasket) on pickup rear fenders (it was used on all front fenders). There is, however, fender welting used as anti-squeak on rear panel-body fenders (Panel Truck, Carryall Suburban, an Canopy Express).

Nonetheless, as Jim Carter states, rear fender welt is non-original a "popular extra".

Tim