Next I gave lapping the heads a try. Notice the bright areas. They were the high spots. They are mostly around the bolt and screw holes where the metal deformed form the tension.
The goal here is to sand enough away to flatten the area where the reed valve seals to the head. I need to put more pressure on the top side where there is more metal.
Either I was getting close or I am getting an uneven surface. Just a few strokes took took off most of the black on the left side
Luckily the area around the valve was in good shape. Here are the two with the old reed valves installed upside down.
I noticed a small bit of rocking between the head and valve plate. By resting both on the glass sheet it seems the valve plate needs to be flattened.