Good catch I was going to tell you how to check but forgot. as far as it being an original its very doubtful but I guess you never know. you can check the amount of stretch by removing your distributor cap and then lining up your timing mark and seeing the amount of degrees it moves before the distributor rotor moves. I can't remember the acceptable number but it is easily accessible on the net. You never know without checking as it could have been done 10,000 miles ago even if it was 1991. Get that zinc in there before you run it again I have seen cams get smoked very quickly on engines that have sat dormant for so long. Again very nice find you don't find them that original and time capsuled that well very often. Must have been stored in a nice dry garage. Also whatever you do to the car just remember it is only original once. One last thing if you do need the timing chain, when you pull the front crank vibration damper you don't need a puller there is a lot of misinformation out there on the web, it is not an interference fit. If it is a little stuck a little persuasion with a hammer on one side while you pull on the opposite side usually does the trick. Look for a groove where the seal rides on the snout if you can catch a fingernail in it then it needs a repair kit and you can get it through your local auto parts store.