FROM DEEP in the packets of yellowing newspaper clippings comes this unwittingly prescient, 29-year-old headline:

"PENNSYLVANIA

AVENUE AWAITS

NEW GLORIES"

Match this with the latest front-page account of the avenue, in which we learn that the best-laid plans for this boulevard still may run into devastating detours: At issue now is how much, if any, low-to-moderate housing--as called for from Day One of the "Grand Design"--will survive by the time Pennsylvania Avenue is rebuilt (if anyone lives that long).

By now, anyone within eyeshot of the creepy, fast-falling-apart Willard Hotel at one end of the avenue, or the creepy, fast-falling-apart Union Station near the other end of this ceremonial street, must assume the worst for the redevelopment plans. More from the clippings:

June 1962: "A dramatic transformation of downtown Pennsylvania Avenue . . . is envisioned. . ."

"If the Presidential Commission's suggestions are accepted, this extensive construction program will leave Washington, by 1972, a pleasanter and more commodious city. . ."

"Daniel P. Moynihan, special assistant to Secretary of Labor Arthur Goldberg, said an action plan to carry out the Pennsylvania Avenue project will probably be hammered out by fall."

December 1963: "The architects . . . now must win President Johnson's support if the project is not to end up on a dusty shelf in the thick pile of discarded grand plans for the nation's capital."

July 1968: "The chairman of the Temporary Commission on Pennsylvania Avenue said last night that the closing of the Willard Hotel may speed the renewal of the Avenue."

October 1969: "The Nixon administration put its support yesterday behind the revitalization of Pennsylvania Avenue first envisioned by John Kennedy. . ."

December 1969: "Presidential aide Daniel P. Moynihan . . . has said that the administration wants the rebuilt avenue completed by 1976 in time for the nation's 200th birthday."

What now? The Pennsylvania Avenue Development Corporation, at last having generated a few visible changes in the scenery along the avenue, will meet in two weeks to settle on a package of significant revisions in plans, aimed at striking a reasonable balance of retail outlets, historic preservation, office space and--here comes the eonomically sticky part--housing for all income levels.

The Reagan administration has not rejected any of these housing proposals, and White House support will be essential in reaching any agreement to include a modest amount of subsidized housing as envisioned over the years. It is not a matter of loading up the avenue with poor people, but of making good on time-honored commitments by four administrations to make Pennsylvania Avenue as functional and attractive as economically possible.