Did the relocation on my 70. First, I took the stock battery tray and drilled out the spot welds for the support portion, leaving the flat tray. I then bolted the tray in place to the trunk floor, drilling a few holes in the trunk floor to accomplish this. YOu can use the stock hold down clamp arrangement to hold the battery in place. I painted the battery tray to match the trunk interior color.
I used welding cable, I think NO. 2. I ran it inside the car, since my interior was out. It feeds over the wheel housing, behind the quarter, then through the sill area. It comes out of a hole where the rocker ends at the base of the cowl area. This is a factory hole. I put a grommet in the hole to avoid cutting the cable with the metal (chafing). It was tuff to route the cable through this hole, but could be done. I think I ran a piece of rope through it first, then tied it to the cable and pulled it through. Once under the front RH fender, I routed it up around the coil spring cover, then mounted a MOrosso battery shutoff switch there, pretty much behind the solenoid. I then drilled a hole in the apron and pushed the cable through the hole about an inch, directly behind the post of the solenoid. Bolted it right onto the solenoid. I wrapped the lug in electrical tape so you do not even see it unless you look for it.
At first, I just had a short piece of welding cable in the rear of the car for a ground, plus grounding the engine. AFter a couple of month, I started having difficulty starting the car. Eventually I could not start it unless I put a jumper cable on the negative post on the battery and ran the other end to my exhaust tip. Had to run another length of welding cable from the negative post to the engine. I ran this one out the trunk drop off and under the car. I used the rubber unsulated clamps to strap down the cable to the underside of the car.
The neat trick about this is that if you want to run an MSD, Crane or Jacobs ignition computer and coil, you can mount them on the battery tray in the engine compartment, then drop a hollowed out redtop autolite battery case over the top, hooking up cables to the battery shell. YOu can tap into the underside of the battery lugs as your power and ground sources for the aftermarket ignition. It looks real clean and no one knows you are running aftermarket. Of course if someone tries to steal your battery they are in for a surprise!
good luck.
