The Koppers set was a reproduction for American Flyer, bought from an AF parts supplier. The Hershey was dry transfers, individually applied from a stock sheet. The Conoco and Shamrock are S-scale decals, but where they came from I can't recall at this point. If AF made cars in those names I probably got them from them from the parts man too. I recall the Shamrock instructions saying that the car body was to be silver in color, but I think white looks nicer.
Another way to expand the scale line is to install scale trucks on 4-wheel 7"-series cars. Just snip off the truck sideframe, file to make it perfect, and drill holes in the floor to accept brass rivets to hold the trucks. All these below were 4-wheel cars.
