When you walk into an automobile showroom a year or two from now, would you believe that in order to make a purchase you must have -- courtesy of the federal government -- a car's "crashworthiness performance rating" (that's the relative ability of that particular model versus others to protect passengers in the event of a 35 mile-per-hour collision), or a front end that has been softened enough to provide "pedestrian impact protection," or a warning light on the dashboard that would indicate if any of the tires were under pressure?

That was the way I originally planned to start this column, ridiculing to some degree several regulations set in motion by departing Carter administration officials and published in the Federal Register on Jan. 22 (pages 7015, 7025) and Jan. 26 (page 8062).

My enthusiasm for this approach grew during the week when I received a 350-page book entitled "The Automobile Calendar" from the United States Regulatory Council. It lists no fewer than 70 recent and pending future federal regulations and activities that affect "the manufacture, sale, or use of automobiles and light trucks."

I spotted among proposed rules some that would develop noise standards for medium and heavy trucks; require a new, expanded rear-view mirror; set labeling standards for batteries to help prevent explosions; and require improved strength of side doors. Then there were Federal Trade Commission studies aimed at examining alleged antitrust activities among the Big Three auto manufacturers, the performance of dealers under automobile warranties and new rules to govern used car sales.

Pity the American car, I thought of writing, it doesn't just have regulation on its back -- to steal a phrase from our new president -- it's got the federal government on its front, its top, its bottom and even its insides.

Then, Thursday night, President Reagan took to the airwaves in his economic pep talk and ruined my whole approach.

He did it by railing against the enormous cost of all federal regulation and those specific rules aimed at the auto industry. "Regulations adopted by government with the best of intentions," he said looking sincerely into the television cameras, "have added $666 to the cost of an automobile."

The impression Reagan created, by not differentiating the good from the bad, was that all those regulations had been damaging to the industry and therefore the public.

In fact, a bit of research in "The Automobile Calendar" discloses that at least one-third of Reagan's $666 figure comes from the added cost of one specific rule -- the one that required auto manufacturers to meet fuel economy standards between 1981 and 1984. And it was that regulation more than anything else, many people now argue, that forced the American manufacturers at last to go to smaller, fuel-efficient cars, a move that at least has kept them in business.

To bring the matter full circle, the Jan. 26 Federal Register (page 8056) carries an item from the National Highway Traffic Safety Administration giving advance notice of a proposed rule extending and perhaps expanding those fuel economy standards to the 1985 model year and beyond.

The notice was issued Jan. 19, the day before Reagan took office, and was signed by Joan Claybrook, the Carter-appointed administrator of NHTSA who was anathema to the auto industry.

As the law and regulations now stand, the standard of 27.5 miles per gallon will be required for passenger cars for 1985 and the years thereafter. There was a lot of screaming and howling in Detroit when that was set back in 1977, but those sounds are not heard any more.

As Claybrook points out, the law "allows amending the standard and establishing a higher one," to affect cars built after 1985.

"Improvements in average fuel economy could save billions of barrels of gasoline over the life of the 1985-1995 passenger automobiles and light trucks," the notice says. It goes on to report that NHTSA is working on an analysis that indicates GM, Ford and Chrysler could achieve 40 miles-per-gallon by 1990 and "over 46 miles-per-gallon in 1995."

The industry already has said it would "attain average fuel economy levels in excess of 30 miles-per-gallon by 1985," according to the notice.

But the Claybrook analysis injects the realistic question of whether the U.S. auto industry, which is expected to sustain a combined loss "for 1980 that will exceed $4.5 billion," will have "the capability . . . to finance investments for fuel economy improvements after 1985 when they have strained that capability to make the investments needed to meet the fuel economy standards through model year 1985."

Several new approaches to the problem are proposed for discussion in the rule-making procedure, including tax incentives for auto makers that make additional fuel economy plant investments.

Showing an understanding of the automakers' problems, the notice argues that "the regulatory approach and stimulation of the market demand for fuel economy are not mutually exclusive."

It proposes "a combination of the two approaches . . . that would ensure steady progress in the improvement of fuel economy while aiding the manufacturers to meet the cost of complying with the standards, the demand for more efficient vehicles and the challenge of the foreign manufacturers."

It is hard to believe that the author of those lines, who also have a hand in the questionable rear-view mirror and tire-pressure-warning-light rules, hasn't learned a good deal about the positive and negative sides of auto regulations. In simple terms, it looks on the surface as if we are exchanging the Carter people who wanted regulation to do everything for the Reagan people who don't want it to do anything.

In fact, what the auto industry has needed is some federal approach that's in between.