hello This is Scott,
A rubber lip-type seal with a metal shoulder is pressed into the intake manifold beneath the thermostat Thermostat Seal - 8.0L V-10 Engine
CAUTION: Housing bolts should be tightened evenly to prevent damage to housing and to prevent leaks.
The thermostat is weird , Remember to replace the rubber seal. I hope this info helps, If you need more info -please ask, Thanks Scott.