The T-stat has to have a couple of features one is call "a jiggle pin valve" it allows air traps to neutralize, the other feature is "reverse poppet'
The reverse poppet thermostat opens against the flow of coolant from the water pump. The coolant, under water pump pressure, is used to help the reverse poppet thermostat stay closed when cool to reduce leakage. This type is engineered with a self-cleaning, self-aligning stainless steel valve
The offset thermostat with jiggle pin valves is equipped with a special valve in the flange, which allows trapped air in the system to escape and permits the venting of air from the system when filling it with coolant
Copied those descriptions from the Gates site. I haven't bought a Motorcraft 195 degree for T-bird SC in quite some time, but they had both feature, reverse poppet and jiggle pin.
The jiggle pin must be positioned at 12 o'clock.
Don't quote me on this one I thought our t-stats looked like they were installed backwards, spring side facing away from the block, but the Haynes manual is not showing it that way.
Hope this helps a little