Ok, I do not have firsthand with one of these, but every other car I have seen with a 'rear mount' battery has had some sort of positive 'post' or somesuch under the hood for jumpstarts and such.

If not, there MUST be someplace under the hood to tie in. How about the terminal block that the alternator cable attaches to?

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1986 300E 5-Speed 240k mi.