I don't know if a 104 pin is like a 103 pin. If it's similar, what I did was use a piece of metal that rested against the head on either side of the rail such that plain old bolt and washers used as an extractor tool did not put pressure on the plastic frame of the rail.

If this doesn't make sense to you then the 104 arrengement is probably different from a 103.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD