Earlier this month, Forest City Ratner Cos. began leasing apartment units at 461 Dean, the world’s tallest volumetric modular tower. The Brooklyn, N.Y., 32-story building, formerly called B2 BKLYN, took about two years longer than expected, thanks to factory production and fit-up problems that prompted the departure of the first general contractor, Skanska USA Building Inc. Turner Construction Co. took over early last year. FCRC decided to use conventional delivery methods for other towers in the development, called Pacific Park Brooklyn.