99% of the time white smoke = egr cooler. Head gaskets usually just cause an overheat and degas bottle venting. Replace the EGR cooler and Oil cooler. There is an oil cooler service kit available from Ford that replaces just the cooler element. Why the oil cooler? The coolant flow for the EGR cooler and oil cooler are inline. If one is plugged, no flow. No flow = repeat failures.