The nation's emotional crisis of the '60s seems to have been followed by a general "small-is-beautiful" nostalgia. One manifestation is a sudden concern for "Main Street, U.S.A.," the roots of the American soul. Sinclair Lewis, who thought Main Street stifling, is probably chortling in his grave.

The National Trust for Historic Preservation has launched a Main Street resurgence project.

It would be lovely, of course, if Main Street - the Main Street Booth Tarkington so perceptively wrote about and Norman Rockwell so lovingly painted - could be resurrected, not as a phony tourist trap, but as the living small-town business and cultural center it once was.

But "business" moved to tacky suburban shopping centers and "culture" flickers through the tube. So all that is left of Main Street is Gingerbread, or Mississippi River boat, or Italianate, or Carpenter Gothic architecture.

Most of that, too has gone to hell.

I don't mind the boarded up carcassess of Victorian buildings. The roting porches, broken gables and swaying turrets you see as you drive off the turnpikes can give you the same sort of thrill you have coming across Roman ruins on a hike in Italy.

Nor do I mind the abrupt parking lots in a Main Street row. Paved papadise is as American golden arches.

What hurts are not the bygone buildings but the mutilated ones, the proud old houses that are publicly humiliated with "modernistic" formica fronts, aluminum siding, glazed Bauhaus Box additions or neon signs sadistically struct on ornate facades.

Crude architectural huckstering never helped the economy of a town. It helped kill it. It destroyed not only th e integrity of old buildings, but also the town's integrity - the image of innocense, wholesomeness and honesty.

With its architectural identity the American Small Town, more often than not, lost its physical identity. It became nothing but a road sign and a name on the map. You could no longer find it in the landscape except, perhaps, for an old courthouse lost between filling stations and a J.C. Penney store. The town got lost in the flotsam of urban sprawl, megalopolis, slurb, or whatever you wish to call the mess.

Fake, huckstering "historic restoration" cannot restore identity and lost innocense either. It is another huckster lie. A "colonial" gas light (how the colonists wished they could have cooked with gas!) in front of a Victorian mansion is just as offensive as a crude neon sign.

So I read with some apprehension in an architectural journal that America has been seized with "hostalgie de ica has been seized with "hostage de la rue" (that's what it said), and that "the preservation movement has gone from monuments and mansions to Main Street." Main Street is being "revitalized" form Newburyport, Mass. to Yreka, Calif., Jacksonville, Ore. to Galveston, Tex., the journal said.

Much of this seems to be a new twist to the old Howard Johnson Phony-Colonial Chic. If Disney World can lure them with plastic, why can't Hicksville lure them with newly painted old brick moldings?

But that, Mary C. Means convicned me, is not what the National Trust Main Street project is all about.

Means is the director of the Midwest Region of the National Trust for Historic Preservation, a private organization chartered by Congress. Midwestern Main Streets are her project. And for all her bubbling enthusiasm, she is going about it with the sobriety of a banker. No fake gingerbread for her.

To see what can be done to restore the old charm and health of Main Street, Means wants to know first what can and must be done about the economic life of the town as a whole. She wants to know whether there is local initiative and how it can be fanned. She calls for a complete analysis, not only of the buildings, but also of local politics, building codes, of tax laws, traffic flow, market prospects and everything else that may help or hinder a Main Street renaissance.

Nor does she want the National Trust, or the federal government, or any other remote authority to mess with Main Street. The Trust wants to encourage small-town citizens to want to do the job - themselved. The project is designed to provide motivation, technical knowledge and practical advice.

To provide this, the Trust's Mid-western regional office, under Means and project director Robert A. Carter, has selected to work in - and with - three towns gathering experience and setting an example. The towns are Madison, Ind., Hot Spring, S.D. and Galesburg, III.

Madison, Ind. (pop. 13,000) is on the Ohio River, has a handsome courthouse and a downtown built almost entirely in the Italianate style. The problem is that a new nuclear power plant nearby opens prospects of rapid economic expansion. This may boost historic restoration or ruin the towns esthetic character and quality of life forever.

Hot SPring, S.D. (pop 5000) has no industry but much charm. It has long been a tourist attraction. Close to national parks and other attractions, it has the potential and desire for even more tourists. Will success spoil Hot Springs?

Galesburg. III. (pop. 37,100), the largest of the three, is an industrial and rail center, has a few historic buildings left, which are not stylistically notable. Its Main Street, furthermore , is showing signs of disintegration under the competition of a nearly regional shopping center, with an enclosed mall. Galesburg, no doubt, is Mary Means' toughest problem.

But she does not seek solutions as such. She sees her task as developing a valid methodology (she uses the overused world "process") to be derived from three years of work and study in these three towns, and widely applied.

The work and studying in each town is done by teams consisting of an anchietect, a landscape architect, a real estate expert, an economist and a graphic designer.

The initial approach of each team is to act as a gadfly, mobilize public support, get people together, teach them to work together. When the Galesburg team held its first workshop a few weeks ago, a surprised Mary Means told me, virtually everybody who was invited showed up and stayed to the end. Elsewhere the workshops scored 70 percent attendance.

The project is financed by a total of $276,000 in grants from the National Endowment of the Arts, the Bush Foundation and others.

In addition to helping the three towns, the practical outcome will be a Main Street restoration handbook and a film.

The film is almost ready for release. "It will send the Rotary Clubs charging out into the streets," says Means.

That's what it will take - and more.

For hwo can we restore the architectural character of Main Street without restoring its human character and a sense of quality and individualism?