Stuck truss rod

On the bench is a lawsuit-era knockoff of a 1950s Gibson ES-175DN, the big electric archtop. It has .026 inches of relief at the 8th fret, and the truss rod will not budge, in either direction.

I’m considering trying a heat treatment, or removing the fingerboard to replace the truss rod, or perhaps a compression re-fret.

What would you guys recommend?

Thanks!

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