Sorry to be that guy but....
There is nothing on the engine that ties it to the car except the engine build date being days to weeks before the car assy date.
Any 273 with a build date in the range will be undetectable as not being the OE engine. You will know but that is it
My 67 dart has the OE engine and was rebuilt once. But if it can't be bored again any engine built in the last quarter of 66 will work