Look at the block number date, the intake manifold date, the heads date, and the carb date. If the distributor date is within a few days of those dates, then it is legitimate as a replacement as long as it is a few weeks before the car build date. Check the underside of your front bucket seats for a build sheet, or under the fold down rear seat, or you may even find it under the carpeting. That is the final authority on build dates. I have argued with "so called" experts about originality, and that is one reason I quit going to car shows. Just get a Deluxe Marti report on your car, and all those dates should come to the forefront. They even have original sale date, location, dealership, etc. It helps to document everything you can. I quit worrying about date correct anything after all these years. I was told by a collector that buys multiple cars that if it is the original owner, then whatever you replace on the car during routine maintenance becomes part of the car, and is technically correct as long as you own the vehicle. A service replacement item from the dealership is still technically correct for the vehicle. That is what warranty work was all about back then. It should not degrade the value of the vehicle. Joe-JDC