One of the last hurdles in the 10-year effort to build a new mass-transit station in New York City proved to be too high. The $900-million project to shift Manhattan's Pennsylvania Station transit hub a block west by renovating the landmark McKim, Mead and White-designed post office into "Moynihan Station" had to be approved by the state's Public Authority Control Board. State assembly Speaker Sheldon Silver, one of three voting members, refused to support it. "The Moynihan Station project was a decade in the making with widespread support including that of two presidents, four past and present senators, two mayors and the community," says Gov. George Pataki (R). The state will terminate its relationship with Vornado Realty Trust and The Related Companies, the joint venture developer. The design by Skidmore Owings & Merrill will be shelved. The question is, for how long. Political experts say Silver's move is a stall to give the honors of groundbreaking to Eliot Spitzer, the democratic candidate for governor.