Replacing fender bolt strip

[DWP]

Hope to get out and work on my son's car soon (skinnyhippo) if it gets above 25 degrees.
I got him the body part to replace the rear area where the fender bolts are. Long curved strip.
Any suggestions on here to cut to replace? along the edge where is bends over to the body, or try to butt weld an inch or so over the edge.
The rust seem to be only around each bolt. I can try to get him to post Pictures later.
DWP

[turbobaja]

Depending on how far the rust has eaten away around the bolt holes, I'd be tempted to just cut the bad ones out individually and replace just the damaged, rusted area rather than cutting the complete mounting surface out and welding in a new one. Pretty good chance of warping the heck out of that quarter panel if you're not careful. If the repaired areas can be kept on the fender mounting surface it will be a lot easier to hide and take less work to make it "pretty" once completed. Shrinkage around the repaired areas will still be an issue, so put as little heat into each repair area as possible at a time as you weld. Take your time and give each tack weld a minute to cool before you go back and weld on the same repair area again. You can make a template for each patch piece and cut your repair piece to fit flush with the surface with a clean butt-weld around it. Keep the fit/gaps tight and heat low on the welder to keep from blowing the weld through and making more work for yourself. Slowly grind the welds down to keep from overheating the area anymore and you're all set.