this is an assembly from an 87 i hope this helps:
^there should be 1 small bolt and 2 nuts from the master and then a clevis pin and clip connecting the pedal to the piston. they should all be possible with extension combos, or possibly stuby wrenches. its been awhile but i remember it being a big pain in the mark3...
the below pictures are in my 84 (mark2) it used to be an automatic trans. the assembly are almost the same so it give ya an idea what it looks like down there...
only one nut is visible, the bolt at the very top and the other nut is time consuming...