This is the fin I broke working on things earlier.
Leaking sparkplug insert.
I measured the bore to be 3.725 inches. Just for reference to compare to the big bore diameter.
I sent the heads with crankcases to Truett and Osborn to be reworked. They did an excellent job and getting this head into shape.
The bore was enlarged. The headgasket surface was resurfaced and the threaded holes were spotfaced.
Exhaust port repaired.