You'd need to match the partial VIN on the block to a full VIN which contains the model information. This would be on the VIN tag, build sheet or (I think for 1969) the data tag on the fender apron.
Whether that Dart or Barracuda car still exists, or if any of those components are still with it may never be known. It could be someone is looking for that engine to reunite with their car. Googling the number along with Dart or Barracuda is a starting point.
