Little more than 24 hours after President Reagan revived the B1 bomber, campers full of job seekers began filling the big parking lot next to the beige, windowless buildings of Rockwell International, each person determined to be first when hiring began this morning for the bomber's assembly line.

By the time Glen Murphy, 26, an umemployed chef from nearby Culver City, arrived today, the line that started Saturday night spilled onto Imperial Highway a block away. "At first I didn't believe it, but I came down to see," Murphy said. "Maybe, when you balance it out, Reagan isn't so bad."

In the midst of talk of welfare cuts and impending recession, Southern California tasted the first sweet juices of the Reagan economy. By noon, Rockwell had processed more than 3,400 job applicants and handed applications to 2,000 more, all drawn by the company's promise to hire 11,000 new employes by 1987 to build the 100 bombers ordered by the president.

The Bank of America's economic outlook report, just published, predicts that California will receive $19.6 billion in military contracts in 1982, a 20 percent increase over 1981.

The contracts will include missiles, aircraft parts, ships, electronic machinery and military research, but the born-again B1 bomber is the new star attraction, worth an estimated $10 billion in business all by itself.

A huge blue-and-white banner, clearly visible to busy traffic on Imperial Highway and Aviation Boulevard, directed job seekers to the Rockwell International employment office today.

They lined up patiently, mostly men in their 20s, with some older engineers, and a fairly even mix of blacks and whites.

"I've never seen anything like this, not even when they first announced the bomber contract before Carter canceled it," said Lt. Robert L. Newton, a Rockwell security officer who kept the crowd orderly through the weekend and at this morning's 7 a.m. opening.

Gloria Lewis, 29, sat on the sidewalk holding the two-month-old daughter of a friend who was inside signing up for an interview. Next it would be Lewis' turn to file into the company headquarters, sprawling over concrete-covered land just southeast of Los Angeles International Airport.

Rockwell was offering interviews to lathe operators, designers, riggers, clerical and janitorial workers and dozens of other job categories. But Lewis, unemployed for a year, said she would settle for "anything. Anything that's going to pay."

Rockwell first won the contract for the B1, a new bomber specially designed for very low, rapid flight to fool Soviet radar, in 1970. By 1977 it was gearing up to build 244 planes.

Then President Carter, deciding the B1 was too expensive and too likely to be overtaken by new technology, canceled the project, bringing "complete astonishment" to El Segundo, Rockwell regional communications director Earl Blount recalled. "It was very unexpected," he said, and 8,000 employes had to be laid off almost immediately.

The company employs about 30,000 people now in Southern California, many working on projects related to the space shuttle, but will expand that by a third for the B1. A total of 22,000 new people will be hired throughout the country because of the bomber, Blount said.

In El Segundo, B1 jobs will increase from 1,600 now to 8,500 by 1987. Another 4,000 jobs will be added in Palmdale, on the northern edge of Los Angeles County, where an 8,000 square foot assembly and checkout building will be constructed to put together parts from all over the country into as many as four new aircraft a month.

To make those parts, a Rockwell plant in Tulsa, Okla., will hire about 2,000 new workers and a Columbus, Ohio, facility about 7,000. A General Electric plant in Cincinnati will build B1 engines, and an Eaton Corp. plant in Milwaukee will build the defensive electronics for the plane.

Boeing Co., which may lose more than $10 billion in contracts because of the cancellation of plans to build a "race track" for MX missiles in Utah and Nevada, will keep a contract to provide avionics integration for the B1. Rockwell remains one of the leading builders of the MX missile, which will still be constructed under a new basing plan announced by Reagan Friday.

The new bomber contract could not have come a moment too soon for Southern California, whose aerospace companies have suffered from the slump in the airline industry.

But industry officials said much of the new military contract money, perhaps 40 percent, will go to subcontractors in places like Colorado Springs, Colo., or Grants Pass, Ore., where housing costs are not so high and skilled workers easier to locate.