Germany had the chance to take land from Austria in 1866, though I don't know how realistic it would have been to take anything more than Austrian Silesia or perhaps Salzburg.
There was a pan Germanic movement in Vienna that wanted to see Austria join with the German Empire in the 1870s, 1880s etc. Since the German Empire was a federal empire, Austria could have joined as a kingdom with the same rights as Bavaria, but this would not have been to the dignity of the Habsburgs who would never have done this by choice.
If there is no Ausgleich in 1866, and maybe if the war with Prussia lasts longer, then the Habsburg Empire might fracture sufficiently for Germany to take all of the Germanic lands in a victory, maybe including Bohemia and Carniola
Best Regards
Grey Wolf