Three fittings? That's interesting, the most I've ever seen have been two. I'm no expert but I believe '69 was the first year for the push in 90 degree style check valve versus the screw in style. I've seen a number of cars with the two fitting version where the second small fitting was either capped or fed the cruise control servo. I'm guessing this would be the correct one for you.

Booster Check Valve


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