Radiasing fender lips

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Another option would be to buy a wheel arch patch panel for a 73-91 chevy truck, cut it down to size and use that for your wheel opening. The chevy truck wheel opening has a similar shape to a duster wheel opening it's just a little bigger. Both of these Ideas require welding though. A simple flare can be made with an adjustable wrench, just close it down to the thickness of the metal and use it to pry the edge of the fender out. It would still need a piece of 1/4 round bar welded to it to give it some strength and a finished edge though.