New York ? It’s getting harder to tell the cops from the crooks around here.

Imagine the surprise of 32 mob suspects arrested this past week, including the head of the Gambino crime family, when they discovered that their brother-in-firearms for the last two years was an undercover FBI agent.

And imagine the disgust of New York police officials when a pair of retired detectives were arrested in an Italian restaurant on the Las Vegas Strip, charged with being mob hit men responsible for eight murders and a failed plot to kill Mafia turncoat Sammy “The Bull” Gravano.

The stunning mob stories broke on consecutive days in New York, still the center of the Mafia universe and home of five of its crime families.

Both took on a Hollywood patina: the FBI agent was right out of “Donnie Brasco,” the mob movie starring Al Pacino and Johnny Depp, and one of the two arrested detectives had played a bit part in “Goodfellas.”

The unidentified agent who gained acceptance by the once-mighty Gambino family was uniquely qualified. He walked the walk, a physically imposing guy built like a tank. He talked the talk, too, the mobspeak that helps right guys get made and wrong guys get whacked.

More important to his associates in the Gambino family, the 50-something mob wannabe could deliver stolen watches, jewelry and plasma televisions.

It wasn’t until last Wednesday, when federal authorities arrested 32 of them, that the mob suspects discovered his true affiliation. “They were all shocked,” said Matt Heron, the New York-based FBI official who ran the two-year undercover operation. “I saw some crestfallen faces.”

None was more shaken than Gambino capo Gregory DePalma, a 72-year-old Mafioso who had once posed backstage with Frank Sinatra and since-slain family boss “Big Paul” Castellano. DePalma, dazzled by the undercover agent’s performance, had proposed his induction into the Gambinos; a similar decision on behalf of the undercover FBI agent who posed as Donnie Brasco led to a mob-imposed death sentence for one of his sponsors.

FBI officials identified the undercover agent in this latest case only as a law enforcement veteran and a family man who volunteered for the assignment.

In the complementary case, authorities say ex-NYPD Detectives Louis Eppolito and Stephen Caracappa had joined the Luchese family payroll in 1986.

Eppolito, 56, grew up in a mob family; his grandfather and father were both in the Mafia. He was the wisecracking, flashy and flabby partner of Caracappa, a skinny, mustachioed detective known as “The Stick.”

Eppolito retired in 1990, Caracappa followed two years later, and the pair became neighbors in Las Vegas.

A law enforcement source, speaking on condition of anonymity, said that Eppolito retained mob connections and Caracappa had access to information through his job in the Organized Crime Homicide Squad. An indictment charged the pair worked together to identify three mob informants, who were then killed for their cooperation.

The detectives also were accused of accepting a $65,000 contract from Luchese underboss Anthony “Gaspipe” Casso to kill Gambino capo Eddie Lino, who was suspected of plotting to kill Casso. Gravano, who helped bring down John Gotti, was targeted for the same alleged offense, the indictment charged.