Keep as much original steel as you can, most of the repop parts are tinny and dent easily especially on outer panels that show. I took a look at those scoop panel patches and was not pleased with the crispness of the lines. Your fenders look like they just need a dogleg shaped patch along the back edge and along the bottom. My fenders are that bad or worse and I am fixing mine. The braces in the back of mine were rough, I cut them out carefully, repaired the rusted parts with new steel and put them back in before repairing the outer panel rust spots. Butt welds in my opinion are the way to go, proper heat and wire speed on the mig will get good penetration/strength. The butt weld requires almost no filler after the joint is ground down. Flange welds create a moisture and debris trap causing rust issues down the road. My 2c

Grant