(FORTUNE Magazine) – AS CONGRESS SHUFFLES into action, Washington business lobbyists are doping out changes in committee chairmanships, while keeping up with the latest maneuverings of powerful holdovers like Michigan Congressman John Dingell (see Profile). So far most industry groups breathe easy about the switches, but the House and Senate Armed Services committees give defense contractors the jitters. They're not sure where the new chairmen stand. Wisconsin Democrat Les Aspin, 46, the new House Armed Services Committee chairman, has generally favored more dollars for military salaries and conventional weapons and less for big weapons systems like the B-1 bomber. But in the last session of Congress he marshaled support for the MX missile after the Reagan Administration promised to pursue arms control negotiations more vigorously. Recently, however, he has been tilting against the MX and toward an antiballistic missile (ABM) system that is part of the Reagan Administration's Star Wars proposal. Senator Barry Goldwater, 76, the Arizona Republican who heads the Senate Armed Services Committee, has supported the Reagan defense buildup. But late last year he stunned defense contractors--and the White House--when he announced reservations about the MX. Says a Washington vice president for one of the biggest defense contractors: ''Goldwater has a tendency to shoot from the hip. You never know where he is going to end up.'' Goldwater has already made one decision that is bound to subject defense contractors to closer scrutiny. He is proposing that a task force on procurement, headed by Indiana's Dan Quayle, become a permanent subcommittee. Oregon Senator Bob Packwood, 52, says he doesn't expect the Senate Finance Committee's agenda to be much different under his leadership than it was under Senator Robert Dole, 61, of Kansas, who has moved up to majority leader. Many business lobbyists hope Packwood is wrong. Worried about mounting deficits, Dole scrounged for revenue wherever he could find it. ''Packwood will be less inclined to tinker around with the tax code,'' says Paul Huard, the National Association of Manufacturers' top tax lobbyist. The new chairman gets high marks from business lobbyists for his opposition to taxing the fringe benefits of corporate employees. If taxes have to be raised, Packwood might push levies on consumption. Says Huard: ''That's all to the good.'' As Senate Commerce chairman, taking over from Packwood, Missouri's John Danforth, 48, is sure to create headaches for some business lobbyists, while pleasing others. He is an opponent of domestic-content legislation, which would require that cars sold in the U.S. be made with a certain percentage of American parts and labor. But he favors reciprocity measures allowing the U.S. to retaliate against countries that put up trade barriers for American products. Domestically, Danforth may give the railroads a rocky ride. While in favor of railroad deregulation, Danforth fears that some shippers may get a raw deal. He may be tough on auto companies too, pushing for air bags and more stringent bumper standards. Most business lobbyists aren't well acquainted with William H. Gray III, 42, the new House Budget chairman. They doubt that he'll be as friendly as his predecessor, Oklahoma's James Jones, who championed the accelerated cost recovery system (ACRS), which permits rapid depreciation of assets. But Gray, a Philadelphia Democrat, says he worries about the deficit and has suggested that some government programs will have to be cut. Says John M. Albertine, president of the American Business Conference, made up of fast-growing companies: ''Gray is not talking about new jobs programs. That shows how the agenda has shifted to the right.''