Auto body repair & detailing: 66 mustang wheel wells, spot welds, mustang coupe

Question
im replacing outer wheel wells on 66 mustang coupe. do i need to remove all of the old well. theres a million spot welds where the inner and outer meet. how do i know where the new starts to accomodate the fender

Answer
You can leave the lip, just grind it down so it's not in the way. Set your outers up close to where they belong and clamp. Set your quarters up to the car and move the outer wheel house as to let the quarter fit. Tack weld the wheel house, remove the quarter, finish welding your panels.
The best way is to drill out all your old welds and start clean.