Hmmm .. can't quite figure it completely yet.
One wonders why pre and post 2001 are different if both are balls .. ?
Haynes says that 2002 onwards were balls, prior to that were rollers.
Its tempting to suspect that the change in bearing type .. if there was one .. coincided with a dimensional change .. if there was one.
Oddly enough it was not so much the bearings but the seals which initially were my focus of attention.
I remembered Capo saying that he'd had issues with the seals fouling the rollers and causing unacceptable stiffness.
The seals were the same as the ones in my original link .. and look like this ...
Adding further confusion, Haynes suggest that the lower bearing has no seal, just a washer fitted below it.
And then there's the notion that its best without the lower seal anyway, as it just holds water in there.
The upshot is that I'm wary of ordering anything that isn't specifically listed for my model (yr2000 M750, but regd in '01).
And even then, the listing might be incorrect.
I can see myself ending up hauling it all apart and having a look before ordering.
Ta for the replies though.