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The 34 (as well as many other years) flat head engines have four Welsh plugs in the block surface, that are covered by the oil pan. You can see the plugs in the photo below. It is VERY, VERY possible the 3/4" diameter metal welsh plugs have rusted through and are now leaking coolant. Sometimes the leaks go inside the oil pan and into the engine oil some leak outward. The plugs can be inspected and changed with the engine in the car, but the oil pan has to be removed. There is OFTEN a lot of original foundry sand still left in the rear of the block that can be removed with the two rear plugs are removed. If you do not see the source of the coolant leak when you clean the coolant staining, remove the oil pan.