The oil pump shaft oil seal can be ordered dimensions 9 x 16 x 4 mm. If you are going to replace it, carefully clean where it sits with a non abrasive material.

The spring side of the seal should face upwards when the oil pump is upside down. Make sure it sits properly in its housing.

If I remember correctly, fitting the engine back onto the chassis with the oil pump on is quite tricky as the oil pump obstructs alignment for the front long engine bolt.

I fitted the oil pump after having fitted the engine onto the chassis.

Don’t forget the washer that sits at the bottom.

Sami