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< CLICK > Door rear window channelIf so, reproductions are available. Here are two: American Classic Truck Parts item #DGC-51L "Rear window channel", and The Truck Shop item #51-05803 "Lower rear door edge glass guide."
I bought one for my '54 3100 from American Classic. Perfect fit. Make sure that you use the correct size screw through the door into the guide. I used one too large and broke off the speed-nut type thread but was able to rig it to work.
FYI - I bought window kit #51-05705 from The Truck Shop (upper felt, inner wipes, outer wipes, staples, door division bars) and was very pleased with the fit. I ordered the glass guide but it was out of stock, so I bought from Classic.
< CLICK > American Classic Truck Parts Search for "Door Glass Metal Channels" under "Window Rubber/Seals/Kits - General"
< CLICK > The Truck Shop Bottom row, center column.