Still, eh... Not sure why you'd want to? Maybe the displacement?

No idea if the valves in the M103 hit the pistons in the 104.
The front covers are different for the simplex vs duplex chains. The oil pumps and pans are also different.

If you find a way to put an M103 head on it and make the simplex chain work on the duplex bottom end or make a duplex chain work on the simplex top end, go for it.

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1993 190E 2.6 Sportline