Hope someone can help:

I recently (about 2 months ago) purchased a 68 coupe, and was told at the time that the owner believed their was a 72 or 73 302 4v in the car. Last weekend I pulled the starter to check the casting numbers and got C5AE-6015 and 7D4. To me this means April 4th, 1967. I should note this definetly is not the original engine as the car was a inline 6. So is this a 289 or a 302? How do I tell? Seems to be a 289 based upon what I've found.