the block gets as hot as what thermostat you're using, give or take some, some spots will be hotter than others like right around the cylinders.
so with a 185 thermostat your block only get 185..... give or that a few spots then?
i ask because everyone always talks about using hi temp paint when they paint there upper intake which i would think would be less in temp than the engine block because of it being higher [less heat]and its aluinum.
..........I would use heat paint on anything that gets hot from the engine just since it's made to handle the heat, better than using normal paint and risk having it bubble or peel off or something