[The Art Doctor]

I cut up a scrap right rear fender to made a traceable template to do this exact thing. I just overlay it lining it up using flange bolt holes, the tracing is thus off the thickness of the sheet metal in one direction but you'd never notice that. You will need a reinforcement plate as Kube notes, it is thicker gauge than the fender if I remember and should help ward off cracks. I will look for mine, might take a few days to find and post a pic.