New Kids on the Block producer Maurice Starr seems to be a busy guy. His latest coup, he says, is to have brokered a marriage made partly in Vegas and partly in high school: a Frank Sinatra-New Kids collaboration. Starr says it will happen early next year, when Ol’ Blue Eyes enters the studio to work on his first record since 1984’s L.A. is My Lady. He says Sinatra, 74, will record one song with all five New Kids and one duet with the teen-pop group’s youngest member, Joe McIntyre, 17. ”I never in my wildest dreams imagined that I would get a chance to work with Frank Sinatra,” says Starr, who claims he’ll produce the album. But a Sinatra spokeswoman says the whole project is still ”at the conversation stage” and the New Kids have no comment. Starr maintains that the go-ahead came a month ago in Atlantic City when he played two songs for the crooner.