Check the head gasket and see if the oil hole is open or closed, this might be a better way to blocking oil flow, and be sure you cam will still get oil since you turned the bearings. Cams get feed oil right from the crank, so the bottom oil hole should be aligned.
You might also be able to pound a lead plug into the oil passage to the old heads. I had forgotten the early engines feed the rocker arms through the head studs.
