Fellow vanagon types 
The pipe threads are to short to get 2 regular nuts onto and the nut that holds the cooler to the block are to thin to use as a pair of jam nuts. you would need a pair of 3/4-16 hex jam nuts these are thin enough to get 2 onto the little amount of thread available. this would allow you to change the oring and not disturb the coolant lines
going faster miles an hour    
Bob Donalds 
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