I agree Peter - i thought that they were fitted backwards when i came to replace mine.

Daft as it may look Peter, you can only fit these bushes up to the ribbed section. This basic design is used on the 126, 600 and 850. If you look at say, Axel Gerstl's website, you will see in the picture of the 500 top wish-bone/rubber bushes kit that is how the bushes fit.
According to the 'book of words', If I have interpreted their Italian-to- English 'tech-talk' correctly, my impression is that you tighten up the wish-bone bush nuts (the ones with the split-pin in your photo) with the wishbone HORIZONTAL. Again if I have read it correctly, these nuts are tightened up to between 28.9 and 36.2 ftlb torque. I personally fit them with a generous coating of copper-slip and do not do them up 'graunch' tight.

the hobbler said:

you tighten up the wish-bone bush nut with the wishbone HORIZONTAL. these nuts are tightened up to between 28.9 and 36.2 ftlb torque. I personally fit them with a generous coating of copper-slip .

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That's a useful reminder Tom because I tightened these at the point when they were loaded and this might have affected the durability. I now recall that I originally did the ones that failed completely when the arms were horizontal and I still had the knock. It makes senseto have them horizontal though, because that way a violent rebound will only take the bushes to around the neutral position.
I always use copper-grease with any fixing that I don't think appropriate for thread-lock and the fixings are all torqued by the book.

When I first bought some new bushes for my freshly sandblasted & painted arms, I couldn't work out how these bushes worked. I ended up pressing them all the way home. Needless to say I couldn't use them and ended up buying new arms with bushes already fitted.
Not the best design, cheap and cheerful. Probably OK for the time but not long lasting and robust compared to todays standards.

There is a way round the wish-bone bush problem, but it is a MITE OTT!. I have mentioned the site before, but watch:---"come nasce una fiat 500 da competizione-non solo motori rr". A superb piece of workmanship--but I wonder how much it all cost!

fiat500 said:

They are designed to be locked in place whilst in-situ and I welded them whilst off the car for more precision; so I guess that the rubber is now slightly under tension in the wrong orientation...hence the squeak. I'll live with it, maybe putting some silicone spray on them.

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UPDATE: The squeak soon went.

I go on some fairly rough roads and tracks at times and recently, the knocking has started again. It wasn't as bad as before but was annoying anyway. I suspected that the welds had broken and the bushes were moving in the arms again. But the bushes were still secure and it seems more likely that the internal metal tube of the bush was no longer gripped by the securing nuts so that they were rotating freely around the pivot shaft instead of the rubber being held under torsion.
My setup has the original parts with castellated nuts and large, dished washers. I supplemented these washers on each side by adding an M12 spring-washer at the point arrowed. After torqueing this up, initial impressions are that it;s fixed. But for me it remains an annoyingly weak point in the suspension.

MAL_6656[1] by Peter Thompson, on Flickr