Yes, if you only disconnected the cable from the T Case and did not mess with the speedo cluster, then you did not cause an electrical short.
The cable itself is mechanical & not affected by anything electrical. The electrical part is when you accidentally touch metal (the dash) to the...
^^^
Electrical issue…not at the T Case end, but instead at the speedo end.
When you tilt the cluster to remove the cable from the speedo cluster you have a very high probability of shorting the amp meter to the metal parts of the dash.
If this happens you will ruin your amp meter & be dead...
Usually a simple fix. If your ‘69 is similar to my ‘75, this is what I would do.
1) Disconect the battery! Important.
2)) Remove the cable from the T-Case and at the speedo cluster.
3) Remove the cable from its sheath
4) Clean it up, lube it up & reinstall.
Should get you going, if not…buy...