I think you are probably right.
I think that Busso, was always late with the engines, except, for the Giulietta.
The 1900 was delayed, because on piston supply. The 6C 2600 was delayed, for the 102 series, by cooling problem ???. The V6 was delayed for the Alfetta GTV series.
I can only confirm, you statement. I have neither seen that there should be an aluminium engine for the 2000 Sportiva. That the reason, whey I find John´s info interesting.
I don't think. that three is any doubt, that the reason we didn't get the aluminium engine block for the 1900, was production problems with an engine block of this size.
Talking of series production, not single peaces. The scrap quantity was simply to large, at this time of experience.
On the other hand. I don't think that they would go for a non, aluminium engine block, for the 2000 Sportiva. It could lead to question, on the Giulietta. Can there be problems
on the Giulietta aluminium engine block,( aluminium engine blocks was unusually in high production quantity in 1954), as there is no aluminium on the larger.
And for the 102 series, there was no reason, to think for aluminium 4 cyl engine block. Because the 102 series should have the 6 cyl 2600 engine. Witch is a all alu. engine.
But could the delay, if it was delayed ?,of the 6C 2600, have been coursed by production problems on engine blocks in aluminium. I thins I saw somewhere, that there is 2 different engine block size for 2600, long and short.
But question on what happened in the 50es, is what do keep Alfa Romeo alive