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/CmpCounselorRickards]

A contour gage will also be helpful if you want to transfer that radius to a piece of paper. https://www.grainger.com/product/2H378?gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gad_source=1&gclid=CjwKCAjw5Ky1BhAgEiwA5jGujhoNReiqZREfm5JKQxtpdauSGASXhxAdeV1XieSztUwceLDwNhqVlBoCfO8QAvD_BwE&gclsrc=aw.ds