California and Florida, two key states in the Republican Party's goal of achieving majority party status, appear likely to gain a total of 11 new congressional districts before the 1992 elections, according to preliminary data on population shifts released yesterday by the Census Bureau.

For California, the projected gain of seven seats in the House would be the equivalent of adding the entire House delegation from Alabama. It would give California a 52-person House delegation, and mean that about one of every eight House members would be a Californian.

For Florida, the addition of four seats would be the equivalent of adding Arkansas' House delegation.

The data also confirm earlier projections that Virginia would gain an additional House seat.

With preliminary Census Bureau population estimates for all but four states now available, the lines of the political map of the United States in the 1990s are becoming clear. Those lines, based on final Census Bureau population figures, will be redrawn by state legislatures in time for the 1992 elections, when eight states are expected to gain House seats and presidential electoral votes and 13 states are expected to lose House seats and electoral votes.

The estimates of congressional district changes were made by computer analyses performed by the National Committee for an Effective Congress (NCEC), a Democratic group. The findings were generally supported by Thomas B. Hoefeller, director of redistricting for the National Republican Congressional Committee.

Although still tentative and subject to change, the major probable developments in addition to the projected growth in California and Florida include these:

Two other Sun Belt states, Georgia and Arizona, are almost assured of gaining only one House seat each. Some previous estimates had given each two new seats.

In two unexpected developments, Louisiana is now likely to lose one seat and Washington state is likely to gain one. Connecticut, Wisconsin and Minnesota, each of which was viewed as facing the possible loss of a House seat, now appear likely to retain the same size House delegations for another decade.

Mississippi would barely keep its five-person delegation in the 1990s, while the population of Kentucky appears likely to fall just short of the number necessary to retain the state's seven-person delegation, requiring the elimination of one seat. The projections for these two states, however, could easily change when the final population counts are released Dec. 31. Mississippi would lose a seat if the final population count is 9,000 lower than the estimate; conversely, if Kentucky's final count is 11,000 higher, it could keep its seven seats.

The overall pattern of population shifts appears to clearly favor the GOP. George Bush won every state that is expected to gain House seats except Washington.

According to the preliminary projections, a total of 19 congressional districts would be shifted among the states as a result of the 1990 census. The winners are expected to include Texas, projected to pick up three seats, and North Carolina, which would pick up one. The losers would include New York, projected to lose three seats; Pennsylvania, Michigan, Ohio and Illinois, projected to lose two each; and Massachusetts, Iowa, West Virginia, Kansas, Montana and New Jersey, projected to lose one each.

The states for which preliminary population estimates have not yet been reported include three projected losers, Illinois, New York and Pennsylvania, and one likely winner, Texas. However, to change the current redistricting outlook in these states would require a significantly larger deviation from earlier population estimates than generally has been the case in the rest of the nation.

Two Democratic demographers said that preliminary population counts for heavily Republican suburban areas appeared to be as far below earlier estimates as the preliminary counts in heavily Democratic cities.

These findings, which contradict often-voiced Democratic concern that a GOP-run Commerce Department would use counting techniques to produce urban under-counts, were reported by Mark Gersh of NCEC, who analyzed population patterns in New Jersey, and Kim Brace of Election Data Services, who looked over the urban-suburban figures in Connecticut and Michigan.

The preliminary population estimates released for six states yesterday compared to population sizes in 1980 are:

Alabama, 3,984,384, up from 3,894,000.

California, 29,279,015, up from 23,668,000.

Florida, 12,774,603, up from 9,746,000.

Georgia, 6,386,948, up from 5,463,000.

Indiana, 5,498,725, up from 5,490,000.

Massachusetts, 5,928,331, up from 5,737,000.