Right you are. I did my car last winter - MUCH more rust than this. Some hints: spray the nuts underneath the running board with WD 40, let it soak overnight, if not the nuts can be very difficult to loosen. Undo the nut a little, push the bolt upwards so you get the head lifted off the alu strip. It is coach bolts with dome shaped heads, so you must grab them with a small plier or vice grip and hold them still while you take off the nut from underneath.
I did not manage to get new stainless coach bolts with sufficiently small dimension (imperial, of course...), so I used 3 mm SS countersunk screws/nuts, a little smaller. The heads of these screws were big enough not to go through the remaining square hole after the coach bolt in the alu, but so small that they ended up totally flush with the metal.When putting back the rubber strips start with the ends and work towards the middle, helped by the corner of a credit card. I had some thoughts about galavanic corrosion alu/steel, so I applied a dab of anti-corrosive fluid on each screw. I wll remove the rubbers this winter to check, though.
It was quite a job. Three threads on each side, nine screws each thread - 54 in total. Roadster with twin exhaust, the silencer being in the way under the running board on both sides. The most medial screws were a challenge, had to use a long, thin plier to hold the nut in the right place before ever so gently entering the screw from above, then tightening them.
Not difficult, but very fiddly. I had a good time. Lying on an insulating mat on the garage floor, Mozart on the radio, slowly progressing.....
