Difference: MP 4286900 and 4286899 water pump housings?

I'm sure this is an easy one, but does anyone know the difference between parts P4286900 and P4286899?
Thanks in advance for any help.

could only find the P4286900, Alum B/RB/Hemi water pump housing. Has bosses for early and late engine applications. Drivers side nipple

I noticed that both Jegs and Year One have photographs of the P4286899 casting in their listings for the P4286900 casting. I'm guessing that there can't be much of a difference then, right?

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I'm guessing that there can't be much of a difference then, right?

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I'd be thinking they used the same photo just for simplicity as they're probably pretty close but there must be some difference. I'm thinking when Ma changed anything on a part it got a new part #. I would want to know what the difference is & an email (free/easy to do) to them would be much better than having to return/exchange a part.