Luxury developers revealed this week a plan to construct towers of 74 and 38 stories on the eastern edge of very low-rise Boerum Hill — a proposal of unprecedented density that neighbors will likely fight. “It’s a massive project,” said Howard Kolins, president of the Boerum Hill Association. “Virtually nothing [in the proposal] is a benefit for people living there. You have to brace yourself for a large high rise that you’d rather not be there.” Alloy Development — which bought up the existing buildings on the block bounded by Third Avenue, Flatbush Avenue Extension, and State Street, but was cagey on the details last year— disagreed, citing 200 units of below-market-rate housing in the 900-unit mixed-use complex, which will also feature retail and two new schools — one a 350-student elementary facility and another a new building for the Khalil Gibran International Academy, which will be able to expand from 160 to 350 students.