White House officials yesterday told four conservative southern Democratic congressmen that President Reagan is willing to accept significant changes in his proposed personal income tax cuts and is prepared to begin negotiating a compromise on his tax package.

Provisions that might be included in such a compromise include an immediate reduction in the top personal tax rate from 70 percent to 50 percent, a cut in gift and estate taxes, reduction of the so-called "marriage penalty," new tax incentives for saving by individuals and lower taxes on Americans working overseas.

In addition, top officials said, Reagan would consider accepting a 5 percent reduction in rates for individuals this year, effective Oct. 1 rather than July 1 as he originally proposed. That would be followed by two 10 percent cuts July 1, 1982, and 1983.

Reagan had proposed a further 10 percent cut in rates for Jan. 1, 1982, and 1983, and a final 5 percent cut Jan. 1, 1984.

Delaying and reducing individual tax cuts in this fashion would constitute a major change in administration policy but would greatly reduce budget deficits in fiscal 1982, 1982, 1983 and 1984. Such a reduction in the projected deficits could considerably reassure jittery financial markets that the tax rates would not add to inflation.

The proposals were outlined by high administration officials in the meeting with southern Democrat at the White House, apparently in an effort to get them to prod House leaders into taking the first public step toward negotiations for a tax comproimse, according to sources disclosed.

Source stressed that the provisions outlined by White House were not intended to be part of a formal compromise proposal but merely a list of measures the administation could accept in neogtiations in negoytiaions with the House.

Rep. Phil Gramm (D-tex.), who led the defection of 63 conservative Democrats to give Reagan a stunning House victory on his budget proposals two weeks ago, said the meeting was "an effort to understand just what the White House will negotiate on." Gramm stressed that no deal was struck.

The southerners met at the White House with officials including Treasury Secretary Donald T. Regan, White House chief of staff James A. Baker III and congressional liason chief Max L. Friederdorf. With Gramm were Reps. Charles W. Stenholm and Kent Hance of Texas and G. C. (Sunny) Montgomery of Alabama.

All of the new provisions White tofficials listed yesterday wre part of an alternative tax cut plan outlined weeks ago by Rep. Dan Rostenkowski (D-Ill.), chairman of the House Ways and Means Committee. However, Rostenkowski has opposed across-the-board cut and multi-year tax reductions.

Sources close to the southerns also indicated yesterday that almost half of the 63 democrats who defected on the budget might be willing to support a compromise involving elements cited by the White House officials.

Most of the southerns are opposed to Reagan's full three-year plan, but some say they would support a multi-year cut if the first year's tax reduction were pared to avoid a large budget deficit.

The administration indicated last week that it is willing to compromise, if congressional leaders take the first public step toward starting talks. on Monday, Senate Finance Commitee Chairman Bob Dole (R-Kan.) invited Rostenkowski to an exploratory bargaining session, but the effort resulted in little progress.

Rostenkowski has been busy consulting with other House Democrats but has made no move to begin negotiations with the administration.

Earlier yesterday, Reagan's chief economist, Murray L. Weidenbaum, told reporters the size and timing of the tax cut proposal are "a judgmental matter" and that changing them would not endanger the ultimate success of Reagan's economic recovery program. "I can't get hung up on the numerology," Weidenbaum said.

Publicly, Reagan is stil supporting the full tax cut he has proposed for each of the next three years. His economists have argued that this large a cut is required quickly to stimulate investment and to reduce inflation. Democrats have aruged instead for a one-year cut, differently structured, as being fairer and less inflationary.

Weidenbaums aid that even if the personal tax cuts are delayed, Congress shoud still cut business taxes retroactive to last Jan. 1 to help spur capital investment.

Meanwhile, Wiliam C. Freund, chief economist for the New York Stock Exchange , warned the Senate Finance Committee that program will not generate enough savings to bouy the economy unless the government cuts spending further.

At the same hearing, AFL-CIO President Lang Kirkland blasted the Reagan tax-cut program as "grossly unfair" and apt to "spur inflationary spending. "He urged the panel instead to refund Social Security taxes to workers.