Motor: Camchain Guide Differences!

Never realized this, but there seem to be 2 sizes of camchain roller guide.  One is about 46mm OD and the other is 51mm.

There are 2 parts numbers:  14610-028-000 and -010

But which is which?


[2/21/16 edit]

So Bill from the Yahoo group confirms that the difference in the Early vs Late is the diameter of the hole, which is 10mm and 8mm respectively (which also matches the hole in the cylinder jug).

Also, MisterMonkeyClaw (a favorite eBay seller) confirmed that the guides he's selling are the 50mm version.

So I'm wondering if the much thicker width but smaller diameter 46mm guide is maybe not S90 at all?