Header gasket is Harley Evo ('84 and newer) spec, so pretty common. I've had very good results with the James brand gaskets (hollow copper ring with stainless mesh inside). Much easier to fit than the stock tapered graphite/mesh things.
https://www.jamesgaskets.com/product/jgi-65324-83-cg/ We use something very similar on older gold wings. On a couple of my barn find projects, I have discovered more than one crush gasket when I took off the headers
