I'm not sure on the specifics, but I believe that one of the modifications that MB/Porsche did was to the chassis to fit the engine transmission in there. I don't know if its possible to put the 500e engine/trans combo into another w124 (not .036).

I could be wrong though.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE