I'm replacing a quarter and the rear wheel well on a 66 Mustang. I noticed it looks like the two wheel well halves are seam welded and not spot welded. Does this sound right? What would be the best way to separate?
No, they are spot welded together, but very close spacing spot welds. You can use a cutting wheel on a die grinder to get close, then use a heavy duty sanding disk to clear off all of the outer wheel well that's left. I would not recommend trying to drill out the spot welds there, as the lip has a crinkle on it that would be difficult to drill into.