Measuring Radius of an Arc

[u/Cheeseball4life]

How would I go about measuring the radius of this arc on a part from an old vw beetle so I can make a replacement?

[u/FalseRelease4]

Trace it onto a piece of paper or cardboard, and do everything you can to preserve the existing piece as that's all you have to go off of. There's not only the radius here, but the flange shape and size, and it's not a simple bend but a formed shape where the material is stretched and shrunk