A black presidential candidate, running well in the South and boosted by new delegate selection rules, could come to the 1984 Democratic National Convention with as many delegates as the state of Texas and play a key role in selecting the party's nominee, according to a report prepared for black political and civil rights leaders.

The document, discussed at an eight-hour meeting in Atlanta Friday night, offers the first nuts-and-bolts analysis of the prospects for a black candidacy of the type being considered by a small but growing group who contend that the Democratic Party has taken blacks for granted.

That group is now discussing the possibility of running a black candidate in several Democratic primaries to increase black voting strength at the convention and shift the direction of party policy and patronage.

The report, prepared by the Joint Center for Political Studies here, outlines a workable but risky approach which, if unsuccessful, could drain vital black support from viable white candidates, intensify racial polarization and fragment rather than unify black leadership.

In addition, the report says, because the black vote will be pivotal to the outcome of the general election, most Democratic candidates probably will court black voters before the convention. Consequently, some 100 to 250 of the maximum number of black delegates, 778, are likely to be pledged to the black candidate.

Still, the report concludes, blacks are in a position to exert leverage on the choice of a nominee and his possible election, and poised to play a pivotal role in 15 of 19 swing states.

"A Democratic presidential victory in 1984 is inconceivable without a strong black showing in northern cities and the South," the report concludes.

The report was one of the major items discussed Friday night by about 20 black politicians and civil rights leaders, including D.C. Del. Walter E. Fauntroy and Mayor Marion Barry, who met at the Atlanta airport. The meeting ended early Saturday morning.

"We gathered to ensure as best we can that black Americans are equipped and empowered in 1984 to defeat Ronald Reagan and elect a successor committed to redressing historic wrongs, setting human needs first on the American agenda and reversing the erosion of our civil rights," the Rev. Joseph E. Lowery, president of the Southern Christian Leadership Conference, told Washington Post Staff Writer Art Harris in Atlanta.

Participants at the meeting discussed but made no decision on a possible candidate, Harris reported. The major action taken was to lay final plans for a draft platform to be completed in two weeks and circulated among other blacks and the major announced Democratic candidates, according to several participants.

Another meeting, the third in a series, is to take place next month.

"We didn't go there to decide on a candidate, but to make sure that we were getting the background data to make an intelligent judgment on whether a consensus black candidate is in the best interests of our people," one participant told Harris yesterday.

The strategy paper also apparently led the group to two other decisions.

The idea of running different favorite son candidates in different states instead of a single one was all but dismissed.

The report had recommended against that, saying, "The bandwagon psychology of the primary schedule probably makes a single nationwide candidacy a more dependable means of amassing black delegates in primary states."

The group also urged blacks to get involved immediately in state party affirmative action and delegate distribution plans, which will be critical in determining allocation of discretionary delegate slots.

Blacks would get more seats, for instance, under an optional formula that would give more weight to Democratic voting history than to the number of votes cast. This is because as a group blacks are among the most loyal Democratic voters in America, when they vote.

The report also encourages more voter registration and maximum participation by black women, since women are guaranteed half the delegate seats.

Those who attended Friday night's meeting included M. Carl Holman, president of the National Urban Coalition; Mayors Richard G. Hatcher of Gary and Andrew J. Young of Atlanta; Dorothy Height, president of the National Council of Negro Women; Rep. Mickey Leland (D-Tex.), chairman of the black caucus of the Democratic National Committee, and Coretta Scott King.

The Rev. Jesse L. Jackson, who is among those mentioned as a possible candidate, along with Fauntroy, Hatcher and Barry, was not present. Some in the group said before the meeting that they would not support Jackson as their candidate.

Young, who was U.S. ambassador to the United Nations in the Carter administration, said he is troubled by the notion of a separate black candidacy. He said blacks would do better to endorse a viable white candidate and then become part of the inside team running the government.

The most effective strategy in dealing with the American political system has been that of Israel, Young said--"to get somebody in everyone's camp so that if some one wins, the interests of Israel will always be protected."

Lowery, however, said the insider approach was not always successful for blacks. "Andy was on the inside with Carter, but what did that get?" Lowery said. "All it got him was to the U.N., and it got him fired."