J. Glenn Beall, the former U.S. senator and a scion of one of Maryland's best-known Republican families, decided yesterday to run for governor, and chose Aris Allen to run for lieutenant governor on the ticket with him.

Allen, chairman of the state Republican Central Committee, is the first black to run on a major ticket for one of the state's top two offices.

Beall's long-awaited decision was reached yesterday, according to informed sources, just as another prominent Republican announced her candidacy for the same office.

Louise Gore, who ran against suspended Maryland Gov. Marvin Mandel in 1974, filed a certificate of candidacy yesterday after selecting two Baltimore-area lawyers, Samuel A. Culotta and Edward L. Blanton Jr., to run with her for lieutenant governor and attorney general respectively.

With less than one week remaining before the July 3 filing deadline, the state's Republican Party ended months of speculation and apparent internal confusion by producing two well-known candidates for the gubernatorial race. Since Mandel's conviction on political corruption charges last summer, Republican officials have traveled around the state proclaiming that 1978 would be the year for their party's resurgence.

But the party leaders' first choice as GOP standard bearer, Anne Arundel County Executive Robert Pascal, announced earlier this month, after weeks of vacillating, that he would not head the ticket.

Beall said that pressure for his candidacy built almost immediately after that, and two weeks ago, at a gala party fund raiser for former president Gerald R. Ford, he seriously began considering whether to enter the race.

Once Pascal bowed out, Louise Gore also decided to put together a ticket and an organization as quickly as possible, according to her press secretary. Culotta is a former member of the state House of Delegates and the unsuccessful 1976 opponent of Rep. Barbara Mikulski. For the attorney general spot on her ticket, Gore chose Blanton, an assistant state attorney general from 1965 to 1968.

State Republicans contacted yesterday said they welcomed the news of their two candidates and seemed especially pleased that Beall had entered the race.

"It's an oasis to a thirsty man," said State Sen. Howard A. Denis (R-Montgomery). "We have all been gearing our local campaigns with the understanding we wouldn't have a strong man on top of the ticket."

Maryland Republicans have been particularly eager to take advantage not only of Mandel's conviction but also of what they see as the state's growing conservatism.

"The atmosphere is right. The tax-payers' revolt is just the tip of a strong conservative movement that I think the Republican candidate can best represent. Certainly there are no Democrats on the scene who could voice that kind of concern," said state Sen. John J. Bishop Jr. (R-Baltimore County).

Beall, yesterday, would only say that he was "enthused about the prospect of being governor of Maryland" and that he had selected a running mate. Allen confirmed their candidacy and said they would mate a formal announcement today on the lawn of the State House in Annapolis.

Beall had been hesitant to mount another state-wide campaign so soon after his overwhelming defeat by U.S. Sen. Paul S Sarbanes in 1976, sources said, and he waited until he received assurances from major Republicans that he would get money and organizational support.

Another specter that bothered Beall, these sources said, was the expected revival of discussion about the "Townhouse fund" controversy, are of the major campaign issues of the 1976 senatorial race. During the 1970 senatorial campaign, $250,800 in cash and checks was funneled to the campaign Beall from a secret White House fund known as the "Townhouse Operation."

Beall in 1976 denied that he himself received these payments from White House aide Jack A. Gleason.

There are three other announced candidates for the Republican gubernatorial nomination in the Sept. 12 primary: Carlton G. Beall, a former Prince George's County sheriff; Donald Devine, a University of Maryland professor, and John Hardwicke, a Baltimore-area lawyer.

Like Beall, Aris Allen is viewed as representative of the moderates within the state's Republican Party. He was minority whip for 7 of the 8 years that he was a member of the House of Delegates.

Politics has always come easy to Beall, who began his elected career as a member of the House of Delegates and went on to become a member of Congress in 1968, winning the Western Maryland seat his father once held.

"Senator Glenn," as his father was called, was a state senator, state road commissioner and members of Congress before being elected to the U.S. Senate in 1952.