I want to start off by saying I know there is already a tech article about relocating your battery to the trunk, and I am in no way trying to knock off what Gydyup has posted. He had a wonderful write up, but I intend to take this one a different route.
This tech article will show you step by step how to mount your battery in the trunk, and cleanly route the cables so you hardly notice they're there. Plus, you can do the whole thing for under $50, as opposed to the 75 bucks you would spend at Summit Racing.
First start off by removing the battery and battery tray. There are two bolts you can see from the top and two that bolt to the side of the frame.
Seeing how you need a tray to mount the battery in the trunk, theres no need to go spend money on a fancy billet aluminum bracket, just be creative and reuse the old one.
Got most the paint stripped off and going to clean up some of the rust.
A few slits need to be cut into the corner of the bracket to be able to bend it past 90 degrees.
This square section was cut out to clear the mount for the spare tire on the right side of the trunk. I didn't cut out the spare tire mount because ya never know if you might want to use it later on down the road.
As for a battery box, they're not necessarily required, but ALWAYS a good idea, especially when you have a source of electricity located so close to the fuel tank. A battery box can be picked up at your local Advance Auto Parts (yes I'm promoting my workplace!) for around $11.
I cut two 8" slits down the length of the box to accept the battery tray.
Also drilled two holes on either corner to bolt the battery box to the battery tray.
Everything will be painted once the mock up is complete.
You will still be able to utilize the old "J-hooks" to secure the battery in the box
The will be two bolts that run horizontally into the side of the trunk and two that run vertically, that go through the floor.
Its kind of tough to tell from this shot but I did the best I could with a camera with a quickly dying battery.
We're pretty much done with mock up in the trunk, now its time to route the positive battery cable down the length of the car. I started by punching a hole beside the starter solenoid using a stepped Uni-Bit.
The Uni-Bit will give you a clean, round hole with far less burrs than a conventional bit. You will need to grommet all of the holes that the battery cable pass through and again, you can pick them up at Advance for 5 or 6 bucks.
As for the cable, I used 2 gauge wire that you can get for $1.88 a foot at guess where?? I used some dielectric grease smothered all over the cable and grommet to coax the cable through. (go ahead, insert joke here_____
Its easiest to start from the engine bay and route the cable from there. I went through the hole by the starter solenoid and to the inside of the fender. I used line clamps to secure the cable and keep it away from the wheel/suspension.
For the next step, I pulled a majority of the fender mounting bolts out to pull it away from the car a bit. (no need to completely remove it and mess with gaps and alignments.
This is a shot with the kick panel removed and it shows where the cable will run.
This is what it looks like on the other side.
Don't worry, its only a bit of surface rust.
In order to get a hole drilled in the kick panel area, I used this goofy looking contraption. It was one of those Christmas gifts from your uncle that you think you'll never use.
Believe it or not, this actually worked quite well.
You can then run the cable from the inside of the wheel well to a recessed channel under the lower part of the fender.
It might be tough to make out but this is between the fender and the rest of the body. The red lines show where the battery cable will lie.
Now into the hole we drilled with a grommet and plenty of lube.
Also, remove the passenger side sill plate because the speaker wire and battery cable will run under this.
Sets in the channel perfect with the fender bolted back up.
At the rear of the sill plate channel, cut a 3" section out to allow the cable to run under the rear seat.
It is better to cut a bigger section out so the cable wont have to make such a radical bend. If you'll notice, I needed to cut out a little more because I didn't like the bends it made. It also doesn't hurt to have some sort of insulation or barrier on these two cuts as well.
Next run it under the back seat and out into the trunk.
After that, cut your cable to the correct length and put a battery terminal on the end so you can attach it to the positive side of the battery.
I utilized my old positive cable for a ground from the battery to a flange in the trunk. Be sure to sand off the paint/rust so you have a good connection. I'm going to wrap the (red)negative cable in electrical tape as to not confuse anyone.
You can now connect the other end to the starter solenoid. Simply swedge/solder a terminal on the other end so you can bolt it up.
Stuff all your carpet back in, reinstall the sill plate, kick panel, and rear seat and you're pretty much done.
Now its time to admire your dirty carpet and attempt to vacuum it clean.
That and admire you're work of course.
If nothing else, you've moved about 35lbs from the front to the rear and cleaned up the engine bay.
Thanks for sticking through this and reading the entire thing! Hope this helps!