[Gaz64]

I have yet to see a 58 DCOE carb, so since the photos show DCOE carbs, that list of options must be a misprint.
In the photos, the carb tops and the mounting flange are DCOE, (55,50,48,45,42,40,38mm), versus the upright parallel mounting of DCO 3 carbs that were available as 58mm.
Going by the airhorn (trumpet) size, I'd say 48mm, possibly even 45mm. This is only a 260.