Resistance between the ignition wire (on starter) and switch (key) goes to zero when the key turned like it should. Still can't figure out why my car turns into a brick when I turn the key and why it was running well a few days ago. Problem description after jump.

Okay so. I drove my car Saturday. Yesterday I decided to start tuning the engine (1973 Pontiac 400 in my 1981 Trans Am). It was running and cranking fine for a bit and then all of a sudden I went to turn the key, the starter made one click, and the car lost all power. The electric gauge was dead, the dome lights, ignition, everything was zapped of power. I felt like "Oh, my battery must be dead" so I charged it. It had no effect. The car was a brick. Every now and then I can plug the battery cables back in and get power throughout the car but the minute I turn the key to ignition the starter makes one click and the car bricks again. Went to autozone to have my starter checked, works well. The battery is good and only a couple months old. The alternator is relatively new and works. The ignition switch is working according to my multi-meter. Also the battery cables were getting kind of hot around the battery post area but that may have just been because I was cranking the engine a lot because I was tuning.