Police said Sunday they are looking for an assailant who brutally punched an 83-year-old subway rider as their train was going through lower Manhattan. The suspect started an argument with the elderly victim, and then struck him several times aboard a southbound 5 train as it approached the Fulton St. station around 6:10 a.m. on Dec. 20, police said. The attacker ran away after the bloody confrontation, according to police. He was caught on camera wearing an orange hoodie, a black vest and a black baseball cap, and appeared to be wearing several chunky gold rings on his fingers. Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS. All calls will be kept confidential.