A few replies / comments / additions:
Engines: historically, it is beyond doubt that the 6C3000 design was initiated and "completed" before the 4C1900, the first having been the priority development in 1948, when the smaller one was also planned, but as second priority. The 6C3000 engine was already ready when the management plans changed, dropped the 6C3000 car, and put all resources into the 1900. That was in 1949.
The odd 82.55 mm bore has a simple explanation: in the market conditions then, the easiest way was to outsource pistons from English producers, in this case Hippolite (sp.?), hence the dimensions that make sense if expressed in inches. The later rebore to 1975cc for the "Super" versions was also intended as dispensing with the Hippolite furniture, coming back to metrical size.
I would not agree that the Sportiva and Disco engines have nothing to do with each other. Indeed, one is cast alu and the other iron, from the top of my memory there's also one with dry sump, but still I seem to remember that the design, possibly the whole cyl. head layout/setup are quite similar, thus explaining the Sportiva's output to be midways vbetween the 115 HP of a 1900 SS and the 158 HP of the Disco. Now the 138hp of the Sportiva were intended for high performance, limited production, but yet stock car, while the DV is a pure racer.
While in a mood of disagreeing
, I would stand on Stu's side about reserving the Disco Volante designation to the original, wing shaped cars, including the "Fianchi stretti", extension to the CMs being, IMO, improper. This can be seen as undecidable pedantry, I reckon. I've met once Bianchi Anderloni one year before his death. He impressed me very much as such a sweet, pleasant person, just happy to be there to talk about beautiful cars without fuss. But I'm sorry to say that I remained unimpressed by the contents of his DV book. No important issue about those cars is addressed, and his text is more confused/confusing than anything else. Another league, unfortunately, compared to his Touring Superleggera book. The DV thing has probably been commissioned to him by an editor... So in this case I would not rate this book as an authority for accepting the DV name for all the cars. It's just that, in order to fill the book without real deep analysis, it needed to caver the CMs as well. Many other source, I think Fusi is among them, but did not check right now, instead insist that there's a confusion. Still, when a current classic cars magazine deals with CMs, the "spin doctor" there put "Disco Volante" somewhere in the title hoping for a sales boost...
Stu: yes, I've been back to sources and confirm that, since Fangio, not Sanesi, crashed the CM spider before Merano, this cannot be confused with the following year's crash of the PR. So Fusi is OK with two CM spiders in addition to the 4 Spiders all identified by VIN. And no, I don't know the VIN of the crashed CM spider.
The next question is: why didn't the coupé suit the Merano race? The two spiders were prepared for Fangio and Sanesi, whatever the name of the drivers on entry forms (this of course also raises the question 'why?', but there can be a lot of reasons). Because Sanesi and Fangio both had to race there. The crash led Sanesi to decide himself if he would drive his car or let it to Fangio. Now why not running the Coupé? Entries were decided probably for two Spiders intended to race and one coupé as "muletto", eventually reduced to two cars.
Actually, while I'm 100% OK with the underrating, historically, of the CMs speed and performance, it must also be reckoned that the cars suffered major reliability problems which caused in several occasions serious crashes: several chassis failures in the steering box area; gearbox seizure causing spectacular crashes,... Also a bit of bad luck if you consider Kling hitting a rabbit or someting like that during Nürburgring practice.