A presidential task force that has studied the federal bureaucracy for the past six months will recommend today major changes in the way civil servants are hired, paid, ranked, promoted and fired.

THe proposals, from the Personnel Management Project, will be given to the Office of Management and Budget and the Civil Service Commission. OMB and the CSC will use the task force proposals to help draw up recommendations for major changes in government that they are preparing to sent President Carter later this month. Highlights of the report they will get today propose:

Splitting the federal white-collar work force into two groups for pay purposes.The 750,000 clerical and technical workers would have their salaries adjusted according to prevailing rates paid in their area by local private employers and governments.

The 500,000 professional and administrative workers would continue to be paid a single national wage rate, based on the principle of "comparability" with industry and state and local governments. The Labor Department would continue to make annual wage surveys to arrive at that "comparability" figure and raises would still come due each October.

Establishing a Senior Executive Service made up of approximately 9,000 career, noncareer and political appointees presently in Grades 16 through 18 or their salary equivalents. Those grades pay from $42,423 to $47,500. The SES also would include lower level political appointees.

Agency heads would have broad avthority to hire, transfer and set the selaries of SES members.Workers currently in those grades could elect to remain outside the SES. But new executives hired would have to agree to join it, giving up some of the security now enjoyed by top career executives.

Testing a "merit pay system to improve and reward" managers below the Senior Executive level. Those mid-management people would work in grades that had minimum and maximum salaries, but would no longer be eligible for longevity step increases.

Using "total compensation" (that is, pay plus fringe benefits) when measuring salaries to determine the regular annual "comparability" increase.

Changing the law that now requires agencies to hire people from among the top three numerically ranked candidates. Instead, supervisors could dip farther down on the list to hire individuals who didn't do as well on tests or exams.

Limiting the special preference veterans now get in federal hiring from a lifetime benefit to "a period sufficient to provide adjustment after military service . . ."

Streamlining the federal hiring system to make it faster and easier for agencies to hire the people they want. This would go hand-in-hand with a decentralization of personnel management authority so that agencies could handle more of their own hiring needs.

Allowing federal agencies to set their own job ceilings, within budgetary limits, rather than being required to meet mandated personnel ceilings. This would make it easier for government offices to split some jobs now held by full-time people and assign them to temporary or part-time workers.

Insiders believe that CSC and OMB will make some changes in the task force report, which contains hundreds of recommendations, before making their own pitch to the President. But most of the changes will be minor ones, since top CSC and OMB officials have worked with the task force and had a big hand in making many of the proposals.