The M103 is a 2 valve motor and the M104 is a 4 valve so the exhaust manifolds are different. ( There is a 3.0 used in the SL but it has a M104 4 valve head )

Plus, you will need some sort of fuel enrichment otherwise the motor will go lean and burn up.

I'd be wary of this, first time poster with a get around the language filter screen name. . . ( even with the post it to e bay offer. )