Just look at people's various signature lines and insert some of the details from your car. It's really helpful so we don't have to ask each time.
Also, your signature should state your intentions with the car. Concours has a few different classes.
Or perhaps you simply want a nice weekend driver. Tells us in your signature.
Since this is a concours site, we will mostly answer with the correct concours answer. In this case that means you should keep the 67 bumpers and have them restored since they date-match the car.
It is very expensive to chrome bumpers with my last set being around $1,500 for the pair.
As Marti said, the 68 bumpers are identical. If you have plans for a really good restoration later be sure to keep the originals in the attic.
Date codes for bumpers are discussed further in the library:
https://www.concoursmustang.com/forum/index.php?board=22.0