I had flushed my radiator coolant, replaced the ECT, AIT, upper and lower radiator hose, temp. sender sensor, and of course the THERMOSTAT last week. As for the Thermostat, purchase the Motorcraft Thermostat (KM-1720). It cost me $13.99 from Fordpartsnetwork.com . The original thermostat had a rubber gasket around it. The replacement T-stat also has a rubber gasket around it...so I strongly recommend to just get the Motorcraft type and you do not have to worry about leakage in the long run. After all this job, my temp. gauge rises up to the M and A line and with a peace of mind.