The "Plum Book," a 164-page political guide to thousands of up-for-grabs $25,000-to-$50,000 federal jobs, is due to hit some government book stores today. Republicans anxious to climb into government after four years in the cold are already drooling over the prospect of a peek at the book that, even at $6 for a soft-bound copy, is a guaranteed Washington best seller.

Disguised with the intentionally dull title "Policy and Supporting Positions," the document is universally known as the plum book, because it contains thousands of political job plumbs. In addition to listing nearly 2,000 Schedule C (political, policy and confidential) jobs that range from coffee maker to policy maker to the mighty, this year's slightly expanded edition contains the names of about 800 non-career members of the Senior Executive Service. All of them make at least $50,000 per year. People lucky enough to have the proper clout and poliical pedigree with the Reagan administration are already lining up in hopes of getting a good job with Uncle Sam for the next four years.

Published after each presidential election the plum book is designed to make it easier for an incoming president, and his appointees, to figure out what kinds of jobs they can fill, and who in the present administration they can replace legally and quickly. Four years ago, when the Ford administration prepared the plum book for the incoming Carter people, more than 15,000 copies were sold here in a matter of weeks -- not to mention freebies that went to the transition team, and friends of friends. It is a mark of status to get one free.But smart people happily pay out the six bucks for the dream book, which is to government publications what the Mieman-Marcus Christmas catalog is to the Sears Roebuck and J.C. Penny crowd.

The plum book contains an agency-by-agency listing of all the Schedule C and career jobs in every federal agency, from the White House to the U.S. Soldiers and Airmen's Home -- and points in between like HUD, Transportation, Commerce, Agriculture.

Even people who aren't dreaming of employment with the Reagan administration will find the book a treat. By careful study of the codes and bureaucratic designations, the wise reader can pick his friends (and foes) in government, figure out what they make and what their titles are, and anticipate that most listed in the book will soon be joining the unemployed ranks. In addition hundreds of jobs are listed that are not normally subject to political turnover. These include some key federal scientists, many of Uncle Sam's lawyers -- who are listed in a special category -- and the like.

The main bookstore at the Government Printing Office hopes to have a goodly stock in later today. If you don't like to stand in lines, don't even bother going down there.