Two men have finally been arrested in the 2002 slaying of Run-DMC’s Jam Master Jay, law enforcement sources told The Post on Monday. “It was all over drugs,” said a former investigator who worked on the case. One of the men, Ronald Washington, had long been suspected of being involved in the hip-hop pioneer’s execution-style murder in his Queens studio, the source said. Jay, 37, whose real name was Jason Mizell, was believed to have ponied up $15,000, while a pal put in another $15,000, to buy a total of 2 kilos of coke that the pair then planned to turn around and peddle. Mizell was new to the drug world and just hoped to score a quick buck, around the time of his murder.