Morning all

When replacing my fuel injectors yeayerday i noticed a drip coming from the thermostat housing where it meets the block, unbolted it and pulled it forward cleaned the block face coulnt see any signs of gasket tho?

Im asuming its not a paper gasket so must be some kind if O Ring, quick googles not showing me anything other than complete thermostat housings, in my experenece non gen ford plastic water stuff just leaks