This pic is out of my 87 GSM.
Very similar, but the lower pic gives a basic idea, the 4 upper pics are more complicated, this job requires at least three Spec Tools.
Maybe some one else (Bfit or Sirfixalot) can throw more light on the subject - personally I would not worry about 15mm of play, as you can see the knuckle is large and thus the play would be also.
As long as the bolts in the fire wall and the bolts securing the saddle to the dash assembly are torque tight, all good.