SLT-6 is 0.060 Over - Runs Hot...Why?????

Just run with the cap off for 20 minutes at idle. if your temp is actually HOT. It will be boiling over. If its not boiling over its not HOT. New gauge or proper sender. Can also monitor the temp sender with a DMM and see what resistance its showing. If your impeller is rotted off, you should see little movement in the rad coolant once the stat opens (or lack of stat for testing purposes)