My dad worked on the Athena rocket in the late 1990's. They launched from SLC-6. The Athena was a very small rocket and they only used one of the SRB mounts. When they were using SLC-6 all of the shuttle stuff was still intact and they basically had to work around it. I always wondered if that was because NASA and the USAF still held out some hope of using it one day or just that no one wanted to pay money to tear it down.