I have looked at previous posts on this topic and to no avail. I have a 67 RS/SS. The new battery dains if the car sits overnight After unhooking the positive battery cable, I hooked a test light to the positive post and the positive battery cable. I unhooked the alternator and pulled the fuses one by one rechecking the test light every time. The test light still gets power when everything is unhooked. Everything appears to be grounded correctley. Could it be the red block on the firewall behind the battery or is there something I am missing?

If the power block is extremely dirty is could cause a leak to ground. However, there are a couple of things still tied into the circuit. The solenoid, horn relay, and the power leads to the fuse block. I'd try disconnecting all the leads off the red block and performing the test again. If the light comes on, look towards the solenoid/starter. If the light remains off, reconnect wires back on the red block one at a time. This should give you an idea which line you should be chasing.

Start pulling the fuses out one by one starting with the courtisy light one fist when you get to the circuit where the problem is the test light will go out