General Motors Corp. Chairman Roger B. Smith, in a personal letter to Transportation Secretary Elizabeth H. Dole, has urged the Reagan administration to delay any new rulemaking on automobile airbag systems until an "independent" study has been done to clear up "massive misinformation" about the safety device.

Smith's appeal comes in the midst of the government's consideration of its next move in the long-running airbag case. On June 24, the U.S. Supreme Court overturned the administration's decision to abandon regulations that would have required auto companies to equip cars with airbags or automatically-closing seatbelts.

In striking down the National Highway Traffic Safety Administration's decision, the court said the agency failed to make a satisfactory case for killing the rules. The court said the agency now has the choice of coming up with better reasons for scrapping the rules, reissuing them or coming up with new regulations.

The case was remanded to the U.S. District Court of Appeals here, which originally ruled against NHTSA. NHTSA and Transportation Department officials yesterday said they are considering several alternatives, but will make no decision in the matter until receiving instructions from the Appeals Court. President Reagan's regulatory policy advisers are also participating in the review, officials said.

"The matter has not been returned to us by the Court of Appeals, but we expect that will happen momentarily," said DOT General Counsel James Burnley. "No decision has been made on what to do. Internal discussions are under way. One thing you do not do is prejudge the outcome," Burnley said.

In a letter to Dole last Friday, Smith said, "My purpose in writing is to urge you to retain one, or preferably two, private consulting firms to conduct studies and report their conclusions by a date selected by you as to the airbag and alternatives.

"These firms, of course, would have to be selected on the basis of their unimpeachable credentials for technical and cost-accounting competence and absolute independence," Smith said in the letter released by GM yesterday.

NHTSA and DOT officials had no reaction yesterday to the letter from GM, which has long opposed mandatory passive restraint regulations. Ford Motor Co., the nation's second-largest automaker, had also opposed mandatory passive restraint rules but is now the sole bidder for a multimillion-dollar federal contract for a fleet of 5,000, 1985 airbag-equipped cars.

Smith said in his letter that an independent study is needed to clear up the "massive misinformation" on the airbag issue. For example, he said that "proponents of the airbag still today quote a consumer cost figure of $125 for an airbag system." That figure is "ten years out of date," said Smith.

GM so far has invested more than $160 million in airbag research and has sold more than 10,000 cars equipped with optional airbag systems, the GM chairman said. He said that "at least a decade must pass before airbags or any other pasive-restraint system could be standard equipment on virtually every car on the American road, as seat belts are today."