I have a 1980 300D with a 722.118 tranny with 098161 S/N so that explains why mine has a vacuum modulator... but yours !?

Take a look at the following link that seems to me is implying that all 722.0 / 722.1 / and 722.2 series M-B trannies should have a modulator.
Note that this listing does not make any reference to S/N(s) !??

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=2&Product_Code=58160D

And you say your tranny has NOTHING... no vacuum... no mechanical interconnection to tell the tranny how much you are pressing down on the throttle??

Something is missing from your story... that is unless you have one of those rare Claire Voyant trannies that M-B experimented with years ago… is this possibly a stick shift in disguise?!

Sam