Three eared oil pump?

[CaptonZap]

Most of the big bore kits as illustrated, come with what looks like a three lobed (mounting ear) oil pump. All of the u-tube videos that I have seen that show how to replace the oil pump show a two eared oil pump.
And none of the videos that I have seen showing how to install the big bore kit mention the oil pump, which I assume was included with their kit.
Can anyone explain what the three eared version is for, or why it is included in the kits?
Thanks for any enlightenment.