The assignment, should you decide to accept it, is to make the memoirs of Gerald Ford interesting. Author Trevor Armbrister took that job, and he says the ex-President's story is far from bland. But it's taken some work. He has 140 hours of taped conversation so far, and in a couple of weeks he begins another marathon round of interviewing.

"It's not going to be LBJ's The Vantage Point ," vows Armbrister, who is on leave from his Washington job with Reader's Digest.

Armbrister helped Representative Donald Riegle write O Congress , and he is the author of books on the Pueblo affair and the Yablonski murders. He and Ford shared the same agents at the William Morris Agency, a happy coincidence that brought Armbrister a $100,000 advance for the Ford project. (That's not all gravy; ten per cent goes to his agent and so far Armbrister's expenses, including travel to Palm Springs and Vail, total about $10,000, though he admits there could be more unpleasant places in the world to research a book.)

For several days last summer, Armbrister invited a friend and former White House speechwriter, Philadelphia attorney Jamie Humes, to join him while he interviewed Ford Humes, 42, has been keeping a file of anecdotes about the White House for twenty-seven years, and he claims to have read every presidential memoir written.

"Trevor wanted me to provide the raising in the cake," says Humes. He tossed off historical recollections on the presidency, then Ford used them as starting points for his own observations.

The goal is a memoir that explains the presidency in an anecdotal way with personal frankness, something no President in recent history has managed to do. The manuscript is due for completion in January 1979, but may be finished much sooner.

Footnote : Debts are the least of Ford's worries. He's signed on for a lucrative TV-book-lecture package that could earn him $3 million over the next several years - a far cry from 1974 when, as vice president, Ford had to borrow $10,000 from his hometown bank to meet his living expenses.