ABOVE
The battery box is from Summit. We bought an Optima battery and dropped it into the box, the U bolt in the center holds the battery, but I noticed the top terminals are pretty close to the edge of the battery and just in case the battery shifts front or rearward in the box, I dropped in some wood block spacers all around to keep the battery cables from contacting the edge of the box.
Notice the #4 battery cables are a little long, this allows the box to be pulled out to the side so the cables can be more easily removed. There is very little room to reach the + bat cable when the box is in place. The extra cable does not cause any starting problem. The neg battery cable is grounded to the rear bumper bolt which is inside the trunk just under the tail light housing. Be sure to clean the metal where the cable will contact for a good ground. I see no need to run a ground cable up to the engine, just use the chassis.
BELOW
Add a good ground cable from engine block to pitman arm upper bolt to complete the ground circut.
I wired in a starter solenoid from an 88 Ford to energize the starter cable. The yellow wire triggers the solenoid and is spliced into the factory purple starter wire up front. I made a jumper wire from the starter main lug to the normal ign switch start wire terminal on the starter so when the cable is energized, the starter will run. This method is safer in my opinion, since the large cable is only live when starting the car. The normal power supply wire is the smaller red wire. I ran a 10 ga wire since I had a spool of it handy, but may upsize to an 8 ga wire. When the engine is running, the alternator will supply power for the headlights or accessories, so the wire will only carry a load when the lights are on and the engine is not running, or for charging the battery when it is run down.
I added a 50 amp toggle switch to the battery box, it carries power from the battery + terminal lug on the solenoid to the red 10 ga power wire running to the front. The toggle will totally disable all power to the front of the car, both for anti-theft, and for safety when the car is parked or stored. We haven't totally replaced the wiring and some of it looks pretty hacked up, so this is a good safety addidtion. I may add a circuit breaker to the 10 ga wire after I figure out what load will be on it.
If the engine is running, throwing this switch will not cause the engine to stop since the alternator can power the ignition. A second solenoid would have to be put between the alternator and the car's wiring to isolate it. The solenoid would have to not only isolate the alternator but switch the output to ground so there is no voltage spike. A better method would be to put a small solenoid in the alternator energizing circut and just shut it off, leaving the alt output wire alone.
BATTERY BOX ANCHORING I removed the four corner box bolts, installed longer bolts and a nut on the bottom of the box, this allows the excess bolt thread to extend through the holes in the floor with a nut and washer underneath. The holes on the side nearest the center of the car come out underneath between the frame rail and trunk depression, make sure you center the holes so you can reach them.