If I pull the fuse that the interior lights and horn are on the drain goes away. What else is on that circuit?

 

Might vary by vehicle, year, and options. Tell people what you've got and somebody might toss an electrical schematics your way.

 

1984 Z28, originally a manual shift car. Now has a carbureted bbc, th400, and 9".

 

Aftermarket alarms & stereos often get wired to that circuit one way or another. Anything of that sort, you will largely have to track down yourself.

 

If the car is no longer stock, no one here is going to be able to offer step-by-step troubleshooting. You're going to have to get a copy of the factory wiring diagram (a search of this site should turn one up ), and track that circuit down section by section, starting at the fuse block, one wire and connection at a time until you find what's causing the current drain.

 

Do you have a dash cam, USB charger, bluetooth device or some other accessory plugged in?