Hmm... the 603 was never offered in the 201 so it might be a mixes metaphor. The regular section of the 126 manual says nothing about removing the radiator. However tight, there's enough room to fit a typical 8mm hex key. Then it's just a matter of fitting a length of pipe for leverage. I'm curious to know how you sorted it out.

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