Okay, first off if you have timing marks on the driver's side, it's not a '68 318 timing cover. A '68 front cover will use a cast iron water pump with a driver's side inlet. With driver's side timing marks, it should be using the later aluminum water pump with a passenger side inlet. using the wrong pump on the wrong timing cover will hide your timing marks behind the loser radiator hose and pump inlet, making them very near unusable. Not to mention the fact that if the timing covers were swapped, your balancer needs to have it's timing mark relocated, since it will be nearly 90* off with the timing marks switching sides.
