Interior lights

A delay timer is part of lighting package. That's your problem. The lights are supposed to stay on for a couple minutes with door switch cycle, then go off and stay off until next door switch cycle. timer goes bad lights come back on or just wont go off.
I can't say exactly where under the dash this little bugger is located.

Did the 68 Barracuda's come with that delay circuit? I've never seen one.