Will a 603 drop into a 116?
 

Just curious, how difficult is it to drop a 603 in place of a 617 in a 116?

Sixto
87 300D

since a 617 is interchangeable with a 603 in the w126, it may work. But you'd need a custom drive shaft I bet and Im not sure how you transmission would mount without more custom fabrication.

Pay attention to the front subframe (the bar that goes across the lower suspension) on the W116. The OM617 that works for the W116 (.950) has a smooth upper oil pan that is thicker on the later engines. The OM603 needs to be thin enough in this area to clear the subframe on the W116.