My 1989 240 probably needs the same treatment on the rear. My outrigger was like as shown but a bodge/ pass MOT repair done for £100 but more rotten, like last 4 inches of the outrigger.
It was 3 years ago when I last removed the seats and fixed boot section and no rust showing. Certainly now though when I did the rear brakes last year the chassis was rusty like the pic and at the bottom of the wheel liner.
It's definitely rust that will kill them off, eventually.
If I win the lottery I would give it a full overhaul inc rust repairs and full respray, add aircon and ABS.
James
