I upgraded the starter cable to 50mm squared which should provide enough oomph to turn over the LS7. I installed the positive to the starter a while back, and covered it with a temperature proof sleeve to protect it against the heat.
I decided to run a 50mm cable directly from the battery to the engine block, and then a short cable from the engine block to the chassis. I thought this would be the best for maximum current to the starter. I used a M10 bolt to fix it to the block, and a M8 one to fix it to the already fitted rivnut on the chassis.
I will run the cables into the battery compartment later.