Johnny, It is easy to do. I set mine to 67000 after my restoration. (had 68400 0n it originaly)
You have to pull the speedometer head from the cluster and then the tumblers.The tumblers can then be worked around to the right numbers.
Yours is a 67 and I have a extra 67 cluster if you can't get it let me know and I will set this one to what ever you want and send the speedometer head to you.