I've read the M103 won't fit under the flatter coupe hood.

People have made the OM617 fit, but it is a cylinder shorter. And it is the first cylinder on the M103 that hits the hood supposedly. If that is the case you could attempt the lower the drivetrain.

However 500/560 motors really aren't hard to find nor are they of extreme value and you wouldn't have to re-engineer anything.

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