[Jac Mac]

If its been plugged with a small 'cup' type gallery plug you should be able to punch a hole in the center & screw in a coarse thread screw to remove it. But I have a gut feeling that you have an original mech cam block and those two drilling from the main gallery to the lifter galleries have never been made, in which case you will have to do so in order to run the hyd cam. To do it 'right' & ensure no debris gets into the main gallery to cause future problems its going to have to be stripped-again. Or you have the option of going back to mech cam/lifters on this or both motors.