With the Indianspolis 500 coming up Sunday, nobody knows what is going on. Gasoline Alley is abuzz with talk of law-suits, disqualifications, reinstatements, appeals, rules changes and cheating by the truckload. "Its a farce," car owner-builder Dan Gurney said. "Abraham Lincoln couldn't straighten it out." Chaos reigns. This is the Three Mile Island of greasedom.

The very existence of the Indianapolis 500 may be at stake. One lawsuit by a disqualified owner seeks to stop Sunday's running of the world's most famous automobile race. Worse for Indy, its sanctioning body, the United States Auto Club, is performing a suicidal dance of imcompetence.

"It's an absolute mess," said the fastest driver in the field, Rick Mears.

"USAC created this monster," said Al Loquasto, one of 11 drivers screaming that they were cheated out of qualifying for the $1 million race, "and it's up to USAC to put this monster back in its cage."

It is too late for that. USAC may control this 500 but not in the future. Since practice began this month, USAC has made mistake after embarrassing mistake. A splinter group, Championship Auto Racing Teams (CART), soon will assume control of Indy car racing because USAC's bungling here has convinced once-loyal drivers and owners to defect to the rebellious CART.

Two weeks from Sunday, the Indy cars run for USAC at Milwaukee.

Maybe.

Only seven cars are entered for that USAC event, maybe half the minimum a race should have.

The same day, CART runs the Indy cars at Trenton. Maybe 40 cars will be there, and if Milwaukee is forced to cancel-or puts on a pathetic show-CART will have seized power.

The question then becomes: Does the Indianapolis Motor Speedway deal with US THE SPEEDWAY STICKS BY ITS HALF-CENTURY CONNECTION WITH USAC, the CART people might have their own race on Memorial Day weekend. Mears hinted at that today, saying, "No, I wouldn't run here again under USAC. Maybe I'd find someplace better to run."

No one has ever found anyplace better to run than Indy.

"That's not to say it couldn't happen," Mears said.

The image is melancholy. A handful of USAC loyalists would run at Indy against junk put on wheels to fill out the field. Somewhere else, Mears and Gurney, the Unsers, Johnny Rutherford and Gordon Johncock would run their exquisite Indy cars in direct competition with the race that made them rich and famous.

"It could be the end of USAC but it could be the end of CART, too," said Gurney, one of the CART leaders, indirectly acknowledging the importance of the Indianapolis 500 to every racer. Without Indy, CART cannot survive in the stratospheric financial world of Indy car racing. It might cost $1 million a year to run a single car.

The guess here is that CART's people will control Indy car racing by this time next year and that Indianapolis will say goodbye to USAC, which will have earned its dismissal with a May 1979 performance that ranks with any Chaplin movie for yuks. The Keystone Kops couldn't hold a candle to these USAC clowns who have played out a Woody Allen script in which they wind up being sued by a man whose entry check bounced.

Wayne Woodward of South Bend, Ind., has a legitimate-sounding excuse for the bouncing check-his wife had written checks when he wasn't looking, or something like that-and USAC waited for him to run to the bank. It was only later, when his car was ruled a flagrant cheater, that Woodward filed suit asking a judge to stop Sunday's running of the 500.

Woodward's suit will be heard by a local judge Thursday morning.

The heart of Woodward's suit is that he should not be discriminated against just because he allegedly cheated a lot. Other cheaters, he says, are still in the race just because they didn't cheat as much. Is that any kind of fair? he asks.

All this cheating has to do with popoff valves and wastegate exhaust pipes. By finagling around, drivers cheated for an extra three or four miles per hour. USAC's inspection technicians pronounced the cars legal before the qualifying runs, but afterward several cars were found to be illegal.

A two-time Indy winner, Johnny Rutherford, confessed to his shenanigans. Sort of. He didn't like the word "cheat." Rutherford said, "It's called ingenuity."

When USAC finally discovered how the cheating was done, it did a dumb thing. It changed the rules in the middle of the game. Instead of a two-inch opening in the exhaust pipe, USAC allowed a 1.47-inch opening for some late qualifiers.

And then 11 drivers who had failed to qualify with two-inch openings-and hadn't been given a chance with the smaller opening that would make their cars go faster-started screaming.

Real loud.

What would USAC do now that it was caught in this obvious unfairness? Well, here's a hint: USAC ordered an injured driver, Danny Ongais, out of his car for 10 days but let him back after eight because a USAC doctor said, "Eight or 10 days-it isn't any difference."

Yes, USAC would do something silly with those 11 mistreated drivers. After a brainstorming session, USAC said the 11 could have another qualifying run Thursday-but only if all 33 qualified drivers agreed to it.

USAC had created a monster, as Loquasto said, and now it was disavowing any responsibility for getting the thing under control. Small wonder that driver Vern Schuppan put a sign above his garage reading "Barnum & Bailey Racing."

Of the 33 qualified drivers, four were reported opposed to the second-chance qualifications. One of the four was A.J. Foyt, a four-time Indy winner who believes 33 cars going 200 mph is all the danger he needs. Foyt's decision was announced by his chief mechanic Jack Starne tonight, althoug USAC was not to report the voting until Thursday morning.

Foyt was right in opposing USAC's bailout brainstorm. His decision also reinforced Rutherford's observation on Tom Binford, USAC's chief steward for the 500: "I think he's rather stupid." For his part, Binford said of this cruel May, "It has made all of racing look rather silly to the public."

The president of CART, Pat Patrick, said he wasn't surprised today when USAC announced in midafternoon another new rule, this one concerning a cockpit manifold-pressure control.

"Who knows?" Patrick said. "Tomorrow we may be racing with only three wheels."tEveryone except Patrick laughed CAPTION: Picture, Roger Penske's Car No. 68, which rookie Bill Alsup expected to drive in the 500, was denied a chance to run by officials. UPI