Three Washington architectural firms are the finalists in an innovative competition for a plan to restore the Old Post Office Building. Restoration is estimated to cost $16 million, with the winning architect receiving about a $1 million design fee.

The architects, the Washington Post has learned, are: Hugh Newell Jacobsen, Arthur Cotton Moore and Faulkner, Fryer & Vanderpool. Formal announcement of the three by General Services Administration Region Three is expected Monday. They were chosen from a field of 93 applicants, including some of the country's best-known firms.

When the building was finished in 1899, critics immediately proposed dynamiting it. The structure has survived, it is said, largely because no one has come up with enough money to tear it down. But over the years, preservationists have come to love the eccentricities of its Romanesque style, popularized by the trendy architect H.H. Richardson.

The GSA program would turn the mosty old structure into a central core to bring light, life and energy to Pennsylvania Avenue at 12th Street now undergoing redevelopment.

The redisigned interior of the old building is to be a civic center of government offices above, with restaurants, performing art stages, crafts center and shops below. All would circle the spectacular skylit inner atrium, called the "most glorious interior court or cortile is 196 feet high.

Two of the firms are associated with large, out-of-town architects for the big project. Moore is in a joint venture with McGaughy, Marshall & McMillan of Norfolk, Va., Associated Space Design, Inc., and Stewart Daniel Hoban & Associates of Washington. Jacobsen is with Shepley, Bulfinch, Richardson & Abbott, and Desmond and Lord Inc., both of Boston. All three are consulting with a considerable group of engineers, landscape and interior design experts.

The Washington architects are well-known for their work on historic structures - Jacobsen for the Renwick Gallery and the Smithsonian Arts & Industries Building; Faulkner, Fryer & Vanderpool for the National Portrait Gallery; and Moore for Canal Square.

The finalists have until May 23 to come up with a preliminary design. Each will get a preliminary design. Each will get about $46,000 to cover their expenses. The GSA board will then select one to be the project architect. Construction is expected to begin sometime next year.

Congress has approved the preliminary planning project but the Public Works Committee has to approve and fund the reconstruction.

The competition is an effort by GSA to improve the design of Federal buildings. For years, architectural critics have argued that a competition is the best way to bring excitement to governmental buildings - accused of being a bland, "plan Jane" architecture.

Architecture competions are not unknown in Washington. The most famoius were run by Thomas Jefferson and George Washington for the U.S. Capitol and the White House.

The Old Post Office Building itself has been controversial since it was begun in 1892 to a design by Willoughby J. Edbrooke.

The Columbian Exposition, a year later, however, established the Beaux Arts classicism of white marble colonades as the architectural trend of the period. So when the Old Post Office was finished in 1899, The New York Times called it a cross between a cathedral and a cotton mill Other have not been so complimentary.

The Old Post Office has had its fans, too. Architect Francis Donald Lethbridge, then chairman of the Joint Committee on Landmarks, said in the Early '70s:

"We have acres and acres of academic classicism. But we have damn few Romanesque revival buildings like the Old Post Office. Its high interior space, like a castle court, is mind-blowing."

Architect John Wiebenson and the militant preservationists of Don't Tear It Down held rallies and published plans to preserve the building. As recently as 1971, Arthur Cotton Moore proposed the building be made a tourist hotel.

Sen. Mike Gravel (D-Alaska: led the Senate fight to preserve it in 1972 by threatening to withhold approval of GSA's plans for the Federal Triangle unless the building was preserved. Until recently, GSA had advocated razing the main structure, keeping only the clock tower.

In 1974, Bill Lacy, head of the Arts Endowment architecture division, proposed the building be made into a national arts center, in time for the Bi-centennial. A few months back, the exterior was cleaned, and people since have admired the Vinalhaven, Maine, granite exterior with its grandiose arches, columns and arcaded windows.

The interior centers around the 99-by-184-foot interior court which rises to a once-glass roof 196 feet up. Part of the program is to restore this space so that the roof is once again all glass.

At first the building, as its name suggests, was used by the Post Office, in later years it has had a variety of occupants, including most recently, the FBI.

When the final contracts are signed Monday, the finalists will begin the rush to design known as "charrettee," named afater the handcart in which competition drawings were rushed to final judgement at the Ecold des Beaux Arts in Paris around the 1900s.

But the final winner is bound to be the city, Washington, if the project is blessed by Congress, will preserve and enhance a landmark. And the Old Post Office restoration will be a towering beginning for a born-again Pensylvania Avenue.