So looking at your, now right side up, pics, I've been thinking this originally had a fiberglass body and you were now recreating it in steel. So I went hunting for info and found the REAL reason you are restoring this car. When done, you'll paint it Chalk White to attract all those beautiful Elvis groupies who left lip stick on his dip... um car.
Oh, wait, they would be about 90 now, eh ?? OK, that can't be the reason.

I guess the next question would be, why not use aluminum sheet ?? Seems like it could be easier to form than steel.
Maybe you could get that BMW group to ship over their body panel bucks to use...