I have owned a lot of Mopars in the last 30 years or so and have come across a car one of my relatives that has passed has left me.
They were the original owners and the car only has 40 k on the obdometer.
I am trying to find out why this car has a 273 2bbl that did not seem to be offered as an option. I have had several other enthusiasts inform me that there is no way this combination was available as this was the first year the 273 was offerd and it was mostly put in Darts. Without a serial number to confirm this on the engine block and the build sheet being lost when the back seat was redone back in the 70s because of a cigarette being thrown out the window and ending up burning a huge hole in the seat. Is there any other way to assure my fellow enthusiasts that this weird combo is indeed from the factory?

Thanks in advance!