I believe this may be what you're looking for. This is from the 1960 Accessory Shop Manual:

[IMG]http://imagizer.imageshack.us/v2/xq90/921/SdLl2Y.jpg[/IMG]


1960 GMC 1/2-Ton Pickup Truck
In the Gallery
Updates in the DITY Gallery
Now cruising in the Passing Lane