Miker. Just measured a seal type plunger drive sleeve, and it's a gnat's under 43mm. So looks to be a difference. Your existing slinger sleeve should have a scroll machined on the outer edge,and be a close fit in the crankcase hole. Some reports of this part being supplied with no scroll, just a plain smooth edge. Reducing your sleeve to this dimension is a possible if you have a problem sourcing the correct sleeve. From experience the scroll/slinger arrangement works well enough as long as the scroll grooves are clean and not coked up.
Cheers
Swarfy.