With the edges cleaned up, flanged, and clamped into place, I went ahead and made the pieces I needed to fill the space where the arch was moved away from the cut zone. This filler piece was also step flanged, cleaned up, marked and clamped into position.
Pic 1, This is the bottom rear of the fender filler piece that fills the space caused when the arch was shifted forward on the fender, clamped in place. Notice the top of the filler piece is also flanged, and you can see the blue line that is where the edge of the arch will be, the area between the step on the flange, and that blue line is where the weld bead will be. The weld will fill most of that step and will be level with the metal beyond the step in the flange once ground flat. It is hard to see but the step and the edge of the filler piece has about the same amount of space. Also notice the fairly equal spacing of the clamps.
Pic 2, Actual welding has taken place! This is how I always do a sheet metal joint. A tack on each side of the vice grip clamps.
Pic 3, The clamps are moved to about the middle of the previous clamp location.
Pic 4, Another round of tack welds. again, on each side of the clamps.