I had my W111 A/F housing out with the radiator not too long ago, but just cannot remember the order I installed them. It had to be manuvered a bit to keep from scrathching it up. Might also check the (3) rubber housing mounts. Would be a good time to replace if original. They look very similar (not the same though) as the fuel pump mounts.
If you do remove the venturi housing, be sure to have a new gasket handy in case the old one tears. I used a very thin coat of Permatex #2 on the new gasket just to prevent any vacuum/oil leaks. Since the crankcase breather tube is just before, you can get a bit of oil slime.