Hello, a 530 O ring chain will fit the standard sprockets. The problem is the gearbox casting may be to rich and foul the chain.
If you have some 530 chain you could try it for clearance.
The safe way to do this conversion is to reduce the sprockets to 1/4" and use a 520 chain. If you thin the sprockets remove metal from the inside only.
Once done it should last far better than a none O ring chain, especially if you fit an oiler.
Iwis, Jwis, both are quoted in their literature.Hello, when I bought my twin in the 60,s it was fitted with a Iwis ( I thought it was Jwis). It was the best none O ring chain I have ever had , it lasted many miles. It eventually developed tight spots rather than wearing out. John.