1997 is a split year for the E300. Early ones use the reciprocating pump which is subject to bearing failure, late ones use a rotary pump of which I've not heard of failure. IIRC you're stuck using the kind of pump that came with the engine unless you replace the front cover and IP timer.

OE engines have the number stamped on a horizontal surface of the block just ahead of the IP. Picture of headless OM602 for reference -



Sixto
87 300D