I'm using jrichker's instructions here http://forums.stangnet.com/775820-battery-relocation.html, only question I have is if I use 1 or 0 gauge welding wire for the ground do I need to use the same size for the power? I had bought a battery relocation kit which came with 2 gauge power wire.... I'd like to use that if I can and just buy 1 gauge welding wire for the ground, would that be sufficient?
Well its like a pipe.... if you have a 3/4" pipe that water is going out and you neck it down to 1/2" there will be some resistance... in the case of the 2GA wire and 1GA ground I will think you will be fine if you are not over taxing your charging system.
Make sure you clean the grounding location for the wire on the frame, firewall and back of the block. This way the you don't to use too much 1GA wire....... make sure a good braided ground strap is used on the block to firewall...
Run a 20awg ground and a 1/0 starter cable and see what happens and a few seconds of cranking.
Your main ground should be the same size (if not bigger) than the starter wire (alternator can be smaller).
If you use 1/0 gauge cable for the starter, you need to run a 1/0 (again, or bigger) gauge cable to the rear sub-frame. After that, it's possible to get away with a smaller (I used 4awg cable) gauge cable running from the rear sub-frame to the engine block.
Generally both wires should be the same size. Especially if they run the length of the car, say from a trunkmount.
If you ground the battery to the body, and then run ground straps at the front for the engine and starter to the body, you probably could get away with smaller cable for the ground straps, except the last one body to the battery.
I have not done the trunk mount yet, but I can attest that the wiring to the starter needs to be stout.