...and about your list, I think there were more models by the biggest coachuilders...for example, I think Pininfarina made 4 1900, 3 2000 and 3 2600, Touring made 1 Coupe and 2 spiders with the 2000 ('58) and a 2600 Spider ('60), etc. I'm sure they are all well known and you already know but I don't see them all in the list or they are under a different model. I think there should be a way to id the right model (with the year or some styling features) to help us in the process...
I fully agree with you PJ, this current list is absolutely not detailed enough:
As a reply on your examples, I have the following listed:
1900
PININ FARINA coupé TI (1900L) => 4 or 5 cars were built, but with at least 3 different front grills, so for me => different cars
PININ FARINA coupé => I split this one up in 3 different versions, and then there is also the 1 off that was made for Farouk, the king of Egypt
PININ FARINA cabriolet => there were 2 series of cars that had visual differences
2000/2600
PININFARINA Sestriere I-II-III => there were indeed 3 different versions of this Alfa Romeo 2000 based car (but it is one and the same car)
PININFARINA 2600 621-coupé speciale => yes, 3 versions as already mentioned in one of my previous posts.
2000/2600
TOURING Praho => there is indeed the one off 2000 Praho
TOURING spider => for the 2000 spider, there is the European version, the European version 2+2, the USA version prototype, and the American version called Roadster + a wooden/clay model from 1957. Plus there is the 2600 spider and a 2600 Spider with a modified front.