Some engines the head bolt holes are dilled into the water jackets. The FE is not that type of design. The FE head bolt holes are blind holes (that means they stopped drilling and there is a cast iron bottom in the hole). You can test each hole with an air hose. They should hold air.
Depending on what you use on the threads to seal them, you are changing how far you stretch the bolt at a given torque. You could be making things worse, if you are not getting the bolts to the proper stretch. Torque recommendations are generally given as dry (no lube) or lubed, to achieve the correct amount of stretch. You put RTV on the threads, who knows what the torque should be.
Good luck.
PS
Only the 4 head bolts between the
oil passage and the water jacket, could have a crack from
oil to water. I would only seal those.