It appears as though what Cadillac called the Thermal Vacuum Switch has snapped off previously on my engine and of course no one in the past has replaced it. RockAuto doesn't list (nor does anywhere else) the part until you go into the 1976 Eldorado year. Oddly enough, the 1976 shop manual does not mention anything about a ported vacuum switch under the cooling system or fuel section. It appears all three ports are there, I'm wondering if it is okay to use? Only criteria is that the switch activates and switches vacuum source when coolant reaches 220 degrees as per the 1973 shop manual.