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My airpump seized up (finally) and when it did I needed to replace the tensioner also.
Anyway, all the searching I did talked about removing the whole pump.
I just removed the pulley (3 10mm bolts if I remember) and put on a 48" belt and used the alternator to adjust the tension (2 belt system). ALT sits in the exact same place it did before.
So there you go, remove the pulley and 48" belt. Your result may very.