So for body work on my '63 beetle, what thickness of mild steel should I get? 1.0mm? Less?

Thanks guys.

1.0mm Cold rolled annealed uncoated sheet is the best to get for forming car body panels.

If you can't get it, a second hand old 60's 70's Holden, Falcon, Valiant panel is ideal.

Thanks Hellbus. Is this also known as zinc anneal or is that something different?

That is different. We find zinc anneal is harder to form into complex shapes when making new panels. It makes the difference between 50 thousand hammer hits to form the panel, or double that for the zinc anneal. It can be used for straight edged parts, folded on a sheet folder easily though.

Zinc anneal is much easier to get, so you can use it. Best to sand the zinc coat off the edges before welding.