MCGT

I'm swapping starters in my coupes. the recipient has regular hex bolt on the lower part of the housing, while the donor has a weird rectangular shaped head, which I have never in my life seen before (and I sure as hell don't own a socket for). Any clues/advice on a solution, and is there only one more bolt directly above the housing (I haven't looked up top of the housing with a mirror yet, and my Haynes *spit, spit* is rather "vague")?

Thanks in advance for any help.