Pretty sure these can be converted, looks like the "A clamp" is held in place by a large nut like most makes, though I've no idea where you would get the DIN parts from.
Sure someone will be along with an answer, but in the meantime....
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If you're going over twins and would like another matching Spiro Arctic I've got a first stage (also A-clamp), and two second stages in very good nick that will be going on eBay soon, only selling 'cos I got a shiny new Apeks for crimbo, so if you're interested drop me a PM
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Good luck with the conversion anyway,
Steve