[Autoholic]

One of the Kent-Moore tools that might still be useful around the garage today when working on an Opel is the J-23600 belt tensioner. You can find this tool for sale on eBay. It's mentioned in the charging system (alternator) section of the FSM.

 

[hrcollinsjr]

There is another version that pops up on eBay from time to time that should work as well.

Harold

 

[First opel 1981]

A big wrench on the lockdown tab works just fine.