Rear Diffs - question on 3 different types for 4.4L

[jbfrancis3]

I'm looking to purchase a rear diff from a 4.4L (3.64 ratio). I've found 3 different variations based on different part #'s. Not only that, but part #'s on Ebay differ by one digit from RealOEM!

Some posts on this forum cover nicely the pre-LCI (up to '03) vs LCI ('03+) rear diff differences. I.e. the medium vs vs the bigger case.

But within that pre-LCI run, there's another break point. '99-'00 have one part # and '01 -'03 have another part #. Here's a realoem breakdown using Feb as a test month in format of engine/prod month/part#:
M62 02/1999 1428652
M62 02/2000 1428652
M62 02/2001 7510654
M62 02/2002 7510654
M62 02/2003 7510654
N62 02/2003 7510658
N62 02/2004 7510658
etc.

What's the difference between 1428652 and 7510654? (Not the output flanges - I can tell from RealOEM that they're same diameter). Examples:
02/1999 (1428652): https://www.realoem.com/bmw/enUS/sho...diagId=33_1013
02/2001 (7510654): https://www.realoem.com/bmw/enUS/sho...diagId=33_1013

And THEN, why do used units on Ebay have 1428651 (not 1428652) and 7510653 (not 7510654), respectively, which is a minor difference on that last digit?

(1428651): https://www.ebay.com/itm/17526614859...3ABFBMjsmAhr5h

(7510653): https://www.ebay.com/itm/22493978056...3ABFBM8K297r1h

Thanks