quarter panel replacement

I need to replace the drivers side quarter panel on my 72 dart. I need some advise on where to cut the old off at. Should I cut below the top body line and try to butt weld the new on and drill out the spot welds inside the door frame and tack the new panel in place? Or should I cut around the panel and flange the remaining metal to attach the new panel too? Any advice or pics will be appreciated.