Early a exahust suggestions?

On the "J" heads I had to grind on the lower boss for the head bolts. Sometimes you have to remove the exhaust manifold that is leaking, clean up the mating surfaces and trial fit to see if there is anything that keeps the manifold from sealing to the ports. maybe an allen plug, maybe the boss that the allen plugs thread into. I think the manifold should seal the port as my 66 273 manifold sealed to the "J" heads. I also use Copper colored Hi Temp RTV to help seal the exhaust.