Specifying only genuine Japanese factory specified oil and dust seals will ensure the item being refurbished will remain oil tight and, importantly, no contamination enters the oil/lubrication system or bearings.
Other seals you may wish to consider:
Keep oil and grease in, and contamination out! Japanese factory parts are frequently good value and always great quality! Order all the seals and gaskets you need at the same time and avoid multiple shipping costs.