Federal narcotics agents busted a heroin operation at a Bronx auto shop this month, severing a million dollar supply chain that stretched to Long Island, court records indicate. They raided Mobile Creations, a luxury car customizing shop, on Feb. 7 after nabbing a Suffolk County drug dealer attempting to sell 68 grams of heroin. The dealer ratted out his supplier, who gave up his source at Mobile, at 1631 Stillwell Ave. near Pelham Parkway in Morris Park, according to a complaint filed in Brooklyn Federal Court. The drug task force officers had the supplier set up a meet with James Gainer, who allegedly operated out of the Bronx shop, and arrested the suspect with 500 grams of heroin he planned to sell for $28,500, according to the complaint. They also snatched Mobile Creations manager Robert Bishun after finding 1.5 kilograms of cocaine and 250 grams of heroin hidden in a vehicle at the shop, and $40,000 in cash concealed in a Mercedes-Benz sedan registered to Bishun. The officers seized a .40 caliber handgun, loose ammunition and $30,000 cash from the shop’s office, along with pay-and-owe sheets detailing millions of dollars in narcotics transactions. The complaint charges both men with drug dealing and possession and Bishun with possessing a firearm linked to trafficking. Four drug grinders and a scale were also found in the shop, according to the complaint. The Suffolk County supplier told the agents he met Gainer at Mobile Creations to buy at least 100 grams of heroin a week. Repair shops and auto parts stores line Stillwell Ave., a quiet street that abuts Metro-North Railroad tracks. The facade of Mobile Creations sports colorful signs featuring Bentleys, Range Rovers and other luxury cars. "I just work here 10-6," said Mike James, a mechanic at Mobile Creations, on Monday. "This is a legit shop." "The shop has been around for over 10 years and they do high-end customization of cars," said Javier Solano, Bishun’s lawyer. "They do Lamborghini-style doors. They do $25,000 rims, $30,000 audio systems." Bishun and Gainer are being held without bail and have not been indicted yet, said Solano. Gainer’s lawyer, Lawrence DiGiansante, declined to comment.