So in the 86 I want to move the battery to the trunk, I want to clean up the engine bay some more and get some more weight in the back. Whats the best way to mount it back there and run up the cords? I'm not looking for a chrome mount either, just the best way of holding it solid.

 

Get one from places like Summit racing. Pretty much have everything you need.

One tip. You may want to install starter solenoid in the trunk near the battery, so the cable running through the frame is only hot during the crank up. You need to run a separate Alternator wire, though.