Removing and installing the pedal box is easier when the brake booster and gas pedal are removed. Getting it out is easier that putting it back in place. I have resorted to cutting specific notches (once the assembly is out) on both sides of car's sheetmetal to help facilitate installation. The cutouts cannot be detected once the pedal box is reinstalled. The overall rigidity of the pedal assembly is not affected by the notches in the car's sheetmetal after it it is reinstalled. Without notches it takes two people to wiggle the assembly back in place. I do not have a picture of the notches in my car but here is a digram that our forum member davidnunn provided. David's digram shows a notch on the clutch side. I made notches on both side.
