Nostalgia trip in a VW beetle - that still zips along

''In those days we were the darlings of the public,'' asserts Dr. Carl H. Hahn, chairman of the board of management of Volkswagenwerk AG. ''But now,'' he sighs, ''it's all changed.''

Pointing to the stunning success of the VW beetle in the 1950s, '60s, and early '70s, things were zooming along beautifully for the West German carmaker as Americans took the beetle to its heart.

Beetlemania was in vogue!

And every last one of them was shipped over to the United States from the VW factory in the homeland - a steady stream that seemed never to end.

At one point, Volkswagen of America was selling 600,000 or more vehicles a year in the US, with most of them the long-familiar beetle, which, the VW management maintained, changed every year, but not too much.

Arthur Railton, then head of public relations for Volkswagen of America and now retired on Martha's Vineyard, Mass., used to regale the world's press each year with his descriptions of all those almost unnoticeable little things that had been done to the car to bring it ''up to date.''

You had to look very hard indeed to see what he was talking about. Even then you might miss it altogether.

A really big event was when VW added a gas gauge to the car back in the early 1960s. Up to then the driver would wait for the engine to sputter and then kick a small lever on the floor of the car to give access to a little more fuel in the tank. Then he'd head for the nearest gas station. And you know, I never ran out of gas on the highway.

VW even put out a thin booklet each year which told people how to tell the difference between a 1965 beetle, say, and the '66. Or it could have been the 1969 bug and the '70.

Changes there were, of course, but the obvious changes were few. One thing was sure: The buglike shape itself didn't change - it was the same basic design Dr. Ferdinand Porsche had conceived back in the mid-1930s before the outbreak of World War II.

''We were a one-car company in those days,'' Dr. Hahn notes.

Today the Rabbit is a far cry from the beetle in the way people feel about their car.

The beetle seemed almost cuddly. It almost cried for help and sympathy from the motorist. And people responded by the millions - more than 20 million at latest count. But best of all, it was reasonably trouble-free and would last for a long time. Obviously, there were exceptions, some motorists would declare. ''But after all, it's only human,'' others would chime in.

I still have a 1970 beetle, a spry 13-year-old that calls for little care, still gives about 32 miles to a gallon of regular-grade fuel, and just seems to last and last and last. At last look, the odometer had topped 155,000 miles - that's 155,000 miles - and all systems were working without a hitch.

And remember, that's with the original engine, not a replacement!

In fact, the beetle's biggest charm was its cheap price (about $2,000 for that 1970 bug), reasonable fuel economy - although some of the later-model bugs got less mileage on the road than my 1970 - and it didn't cost too much money to keep in tune.

In fact, the beetle was an ''in'' car all over the world.

But as safety and emissions regulations piled up on VW, the time finally came to ''dump the bug'' and roll out the Rabbit - or Golf, as it is known in the rest of the world.

An instant success, carmakers everywhere copied the Rabbit design and longevity seemed inevitable. Yet, the copycats, together with a faltering world economy and the in-force arrival of the Japanese on the Interstate, sent the Rabbit into a spin and sales plunged all over. US-built Rabbit subcompact sales in 1982 were off a stunning 40 percent compared with 1981.

Better days seem ahead, however, as a Rabbit replacement moves closer to the marketplace.

As for the VW beetle, however, it refuses to quit and continues to be built in several countries around the world. Sales of the Mexican-built beetle are soaring, Dr. Hahn reports, and VW drove off with about 45 percent of the Mexican car market last year, mainly because of the beetle's success. A year ago it had 30 percent.

''We are now manufacturing 800 beetles a day in Latin America,'' Dr. Hahn says, perhaps a little perplexed at the vehicle's continued appeal even as the Rabbit hops downhill.

Of course, you can't buy a beetle at a VW car dealership in the US today, because it doesn't meet all those federal regulations.

Even so, an enterprising group in California is now ''federalizing'' the Mexican-built beetle and selling it in the US for $6,995, plus accessories, according to Automotive News, the trade weekly. There's no warranty for the new car, however, according to a VW spokesman, because it is neither built nor sold by Volkswagen of America Inc., a subsidiary of Volkswagenwerk AG of West Germany.

Nonfederalized beetles - that is, VW beetles that do not conform to US safety and emissions standards - cannot legally be brought into the US.

Meanwhile, would I voluntarily get rid of my 1970 VW bug? No way! With no penetration rust on the car, and a quite-good-looking finish on the outside, it makes no sense - to me, at least - to push it off the road.

Also, its value is on the way up. While it may be worth $1,500 or more in the marketplace - and it only cost $2,000 to start - the depreciation amounts to less than $50 a year.

Where else can you find that kind of a car bargain these days?