Sorry - Inexplicably the post notification went to spam, so I missed your reply.

I was talking about the big O ring inside the clutch housing - the one that goes over the crank shaft - about 100 mm diameter. In the end I just popped it in with a good dollop of silicon grease. I assembled the flywheel and clutch and ran the engine minus the gearbox for about 30 minutes and didn't see any oil coming through either the main crankshaft seal or the O ring, so fingers crossed I got it all OK.

The gearbox went back in OK (tricky when working alone!) All appears to work OK, but first and second are a bit stiff to engage. I am hoping that things will ease up once I have a few km under her belt. The modified reverse flappy thing works OK too.

So - in summary it is possible to rebuild a S3 Suffix B as a Suffix D. Time will tell if it is actually any better!

Thanks for everyone's help/interest.
 

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