RE: The second pic, showing stop lever near transmission vac modulator.
The gap is supposed to be 0.5 mm. Not closed.
Before you set out to adjust the levers by loosening the locknut and rotating the linkage sockets in and out to change lengths, measure the linkages carefully and make a sketch of them, then when things are worse after changing them, you can get back to factory setup.
I have seldom found any engine performance increase from changing the gap at the stop lever. Sometimes the idle speed is increased after messing with the linkages, and the transmission shift points can be changed also, so do a careful road evaluation as you go with this kind of thing.
Note also that the linkage bushings can affect how far the IP is driven from a given accelerator pedal pressure. If the plastic bushings are elongated, some of the pedal movement is translated into sideways movement in the linkage. Simply replacing a worn pivot mount bushing will get you improved acceleration at a small cost. check item 45 on p.20 FSM see:
http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Engine/617/30-300.pdf
But watch out that server is SLOW!