Battery relocated in trunk.

Guys - I appreciate the input as this is precisely why I asked on here! There are a myriad ways to wire these things. While the system I have will work, I still hope I never have to test the overall safety aspect of it but this system will kill the engine via the rear-mounted master switch and it has fuses on anything that runs power forward or rearward from the battery to the front of the car.

@crackedback - your idea of a welded nut for ground attachment and a CD relay powered after the cut-off switch as the link between the alternator and battery is a good one. Like you said, it keeps the alternator isolated for charging and kills it too when you throw the master switch. I like that idea! Likely better for the battery drain too since this is a single-wire alternator car and I've heard they can sometimes have a small continuous draw.
I assume you choose the 1/0 welding cable just due to the better flexibility of it?