Where is my heater core located?

Its probably up underneath the dash. On most vehicles your have to remove the dash

This is not even close to a DIY repair! .. Strongly suggest professional hands-on testing to confirm overheating problem .. Antifreeze would have to be pouring out of the heater onto the floorboard IF the heater core were the culprit! .. Hint, the 'heater hoses' hook up to the heater core..... Good luck with it!