340 engine timing issue

i am helping a friend get his challenger out of hibernation..it runs a little rough so i suggested we check the timing..when i put a light on it i cannot locate the timing marks no matter how far we swung the dist?we did remove the dist drive gear to prime the motor..it has a stock cam and new chain..and the motor is fairly fresh.it always ran well from what he says.is it possible when he reinstalled the drive gear he is off somehow? suggestions?:read2: