Bravo (Classic) Hello Fiat Forum plus historical query

[500Tigre]

Hello all, currently own an old 2001 Fiat Bravo 1.6 SX 16v and have not had much issues with it aside from the usual wear and tear.

Am interested though in reading up more on the classic Fiat 500 and was wondering if anyone here who has currently got Dante Giacosa's book - Forty Years of Design with Fiat or any other comprehensive sources could answer a query I have relating to the old Fiat 500?

On page 323 in a letter Dante Giacosa mentioned the following in the context for what eventually became the Autobianchi A112:

I have also given thought to a version with an air-cooled engine. This has resulted in the planning of a two-cylinder horizontal 850 cc engine with a special design having a piston-balancing mechanism (studied some time previously and now improved). This engine could also find military applications and could possibly be considered for long-term development of the 500, fitted with an automatic gearbox.

Interested to know more about this proposed air-cooled 850cc engine? Additionally going back to the classic Fiat 500, is it known how much viable enlargement was left in the Fiat 500/126 air-cooled 2-cylinder engine beyond 704cc?