A frustrated Chrysler Corp. Chairman Lee A. Iacocca showed reporters a roomful of Chrysler cars of the future, insisting they could beat the competition from Japan and other foreign and American producers if the company gets the chance.

But in a long monologue spiced with four-letter words, the Chrysler chairman said the Carter administration and Congress lack the political courage to single out the American auto industry for the special help it may need to survive the worst depression in auto sales in 50 years.

He renewed his call for a $1,500 tax credit for motorists who buy new American-built cars and trade in pre-1976 gas guzzlers but saw no hope of getting such help.

Although the leading indicators of the auto industry's health have shown signs of improvement in the recent gains in used-car sales, new light-truck sales and credit availability, the economy's recovery from the current recession will have to be prompt and strong to generate the sales the industry needs, Iaccoca said.

At current sales rates, General Motors Corp., Ford Motor Co. and Chrysler could suffer a combined loss of $4 billion in 1980, Iacocca said, quoting figures "bandied about by the secretary of Transportation and others."

The demonstration of Chrysler models for 1981 through 1984 at the company's headquarters here was intended to show that Crysler -- whose survival has a times been counted in days -- has a future.

"We have our onslaught coming as well." Iacocca said, pointing to the showroom where a ring of future Chrysler products were on display, The line-up began with the new midsize, front-wheel-drive K cars, which will go on sale this fall and which Chrysler says will get 40 miles a gallon in highway use. Also included was a 1982 front-wheel-drive pickup truck, a 1983 sports car that resembles a Porsche, and a 1984 downsized van, bigger than today's station wagons but smaller than today's vans. Iacocca's press conference today was the first full response by an auto industry chief executive to the auto aid plan outlined by President Carter in Detroit a week ago.

Iacocca said that it offers little except for immediate financial help from the Small Business Administration for hard-pressed auto dealers. He said the rest is promises.

Iacocca's chief complaint is the flow of Japanese imports which now account for one out of every four cars sold in the United States. He wants these imports cut by one million cars for a two-year period until the American producers recover.

"The president assured us at the breakfast here that he would quietly give them the word," said Iacocca, meaning a warning to the Japanese to limit their auto shipments voluntarily. The president also spoke of a comprehensive tax package next year that would help the automakers and other troubled industries, and urged the auto executives to be patient.

"I said, 'Wait for that? We are all going to be dead." Iacocca recounted. At the meeting with the president, Iacocca plugged for his $1,500 tax rebate plan, one which he said nearly would pay for itself by speeding the economy's recovery and increasing gasoline conservation in the United States. e

"My program is really simple," he said. The $1,500 tax credit would go to everyone who purchases a fuel-efficient new car and trades in a pre-1976 car. Because the older cars average considerably fewer miles per gallon than the new cars, the switch would reduce gasoline consumption substantially, he said.

He contended that 1.5 million new cars would be sold between now and Christmas with the program, resulting in 200,000 auto workers returning to jobs and several hundred thousand more laid-off workers now unemployed in related industries. The cost would be $6 billion, but higher income tax and Social Security taxes and a reduction in federal aid to the unemployed would offset all but $2 billion of the cost.

That $2 billion could be covered by a penny-a-gallon tax on gasoline, he said.

"Slap it to them and you get this industry picked up by its bootstraps," Iacocca said. "They said 'terriffic, except politically, we can't do it.' I said, 'Well then, you lose your ass in the election. It's not me."