Gerald R. Ford's name was placed on the Maryland presidential primary ballot today, setting up the state's May 13 primary as one of the former president's first electoral tests should he make a belated run for the Republican nomination.

Secretary of State Fred Wineland, a Democrat who has the sole power to decide which candidates and would-be candidates appear on the state primary ballot, dispatched a letter to Ford this afternoon informing him that he would be on the GOP list unless he withdrew by March 21.

In the last few days, Ford has indicated that he is ready and willing to get into the race if enough Republicans seek him out as an alternative to the latest front-runner, Ronald Reagan, who Ford contends could not with the general election.

Although there are 18 state primaries between today and May 13, the filing deadlines have passed for all but three of them. The deadline for two of these three, in Indiana and the District of Columbia, is this Friday, before Ford is expected to decide on whether to run. He might be on the ballot for Tennessee's May 6 primary.

"If Ford decides to go, Maryland could be his starting place," said Allan C. Levey, the Republican chairman. "And it wouldn't hurt the party if he got in, while it might help."

In 1976, Ford trounced the conservative Reagan in the Maryland primary, winning every delegate to the Kansas City convention. The prospect of his campaigning in Maryland again this year is being hailed by many in the state's moderate Republican establishment who, until the New Hampshire primary, were lining up behind George Bush.

Republican politics have taken on such a mercurial nature this year that many moderate Republicans appear ready to jump from Bush to Ford after only one Bush disappointment, his loss in New Hampshire. Among those is state Sen. Edward J. Mason, a prominent Republican in Western Maryland.

"I think Ford could win in Maryland, and I'm glad to hear he'll be on the ballot," said Mason. "Ford's been my man all along. Without [Ford] on the ballot I'll have to see if I can run as a Ford man." Only three weeks ago, Mason announced his intentions to run as a Bush delegate.

Party chairman Levey, who privately was pushing Bush's candidacy before the New Hampshire plummet, is expected to line up with Ford should Bush and another moderate candidate, Sen. Howard Baker of Tennessee, do badly in today's primaries in Massachusetts and Vermont.

Levery, like Ford, is an alumnus of the University of Michigan, and they have been close associates for several decades. Four years ago, Levey served as a fund-raiser for the former president.

The chairman's interest in a Ford candidacy became apparent Friday when Levey's assistant at state party headquarters. Tom Buckmaster, placed a call to Wineland urging the secretary of state to include Ford among the primary candidates on the ballot. According to reliable sources, the call was made at Levey's request.

The state's highest elected Republican official, U.S. Sen. Charles McC. Mathias has been predicting for several weeks that Ford would enter the presidential race. According to sources close to Mathias, the senator has expressed fears that Reagan might win the state primary unless moderates and liberals united behind a candidate such as Ford.

But while many uncommitted Republicans and some Bush supporters were clearly looking forward to a Ford candidacy, the chairman of Sen. Baker's campaign committee here was embittered by Wineland's decision to place Ford's name on the ballot.

"I'm shocked," said Baker's man, Sen. Howard Denis of Montgomery County. "It's [Wineland's decision] mischievous . . . meddling in Republican presidential politics."

Denis said he would ask the state attorney general's office to issue an opinion as to whether Wineland was exceeding his authority, of Ford, Denis said: "I have the greatest respect for him, but of course of all the potential candidates, he was the only one to lose to Jimmy Carter. This vacillation and agonizing reappraisal of his is doing the party no good."

Levey, on the other hand, said Ford's entrance into the race would help the party. "It assures that the convention (in Detroit next August) will decide our nominee." said Levey. "I think it would be bad for the party if the mominating process was over before the convention."

Along with Ford, Reagan, Bush and Baker, Wineland placed U.S. Reps. John Anderson (R-Ill.) and Philip Crane (R-Ill.) and Sen. Robert Dole (R-Kan.) on the Maryland ballot. c