Reply to "Brake Booster"

From the photo, it seems as if the booster itself is fine but the long extended master cylinder reservoirs & caps do indeed get too close. FWIW, I usually recommend the adaption that uses the GM step-cylinder with crosswise fluid reservoirs. This booster is slightly bigger than stock but nothing gets close to the lid.
OK- I wouldn't expect washers to work because the booster actually bolts on with a triangular pattern. But an angled plate should do the trick. This will require you to dismount the whole booster, make a pattern, cut the angled spacer etc. Another option is to tilt the whole pedal mounting plate, and I don't know if this will cause problems with the clutch or brake pedal travels or not. You could try it, in the garage & see what happens. Again, washers won't work because they will expose a wide crack from the front trunk to the passenger compartment and you may get nasty drafts in as well as radiator heat if the top plate & seal aren't perfect. This also properly should be done with an angled plate.