Bad timing chain ?

anyone know of a way to find out if a timing chain or gears is bad without tearing the front of the engine apart? My son just picked up a 73 duster orig 318
59000 miles on the odometer I think it has turned over once..... he put new plugs in it and it has been running fine for a couple days, he went out and started it after work and it has a idle miss .I pulled all the plugs and they look fine,and i checked the timing and its fine. when he drives it he said its pinging now that its running bad.