Rear quarter body help needed

Do you know what kind of machine it takes to do a proper ERW weld? Those 220v Lenco's and hand held tong welders don't provide enough clamping pressure or have enough *** to barely get 2 pieces of 18g stuck together never mind welding in a heavier gauge rocker where there's 2 or 3 layers involved. You going to have 460v service installed and buy a $15k resistance welder so you can do a factory correct looking repair because anything else would be a bullshit repair or you going to use the Mig you have and dress the welds because maybe you had a little trouble pulling off a perfect weld laying on your back welding upside down?