It's possible that the one cable wasn't the only problem too. Also, it's possible that the crimp wasn't tight enough and the cable just isn't moving the end.
The speedo is easy enough to test, pull the cluster, and use a dowel (sanded square) in a drill to drive it. Remember, it won't read if you're running it backward.
With the cable a too long is better than a too short. 1/8" shouldn't matter, but 1/4" or more would. Are you sure it's securely mounted to the green basket (or whatever you want to call it)?
EDIT: When you pull the cluster to test the speedo, try turning the cable's spindle by hand... if it moves more than a quarter turn or so you probably have another break somewhere.