How should I go about repairing this?

[eastcoastjumper]

My b pipe head pipe has been leaking some oil for a little while now. I kept blaming the gasket and replacing one after another and it just kept leaking. Almost had the manifold and head pipe milled, until I found the cause. It's a shame because I recently had it powdercoated, and it's an xscream ported big bore setup.

Found it using brake clean and watching it dry, thanks for the tip @JetManiac @Blue

 

[Dartman]

clean it well
weld from inside only
use an highly experienced welder with good tig welder
don't grind just leave weld bead
you won't even know the difference