So per Rob's suggestion (
@crackedback ), I had used red 1/0 welding cable for the hot wire coming from the battery in the trunk. I ran that through a "Ford" style relay so that it is only hot when the starter is being activated. That way, you don't have to worry about the cable becoming grounded and causing a huge short as the car/wiring ages.
I also have a 1-wire alternator and used a 4ga wire for the alternator charge wire going to the battery. It is fused both up front in the engine compartment as well as right by the battery. This is so it is protected should a short occur near either end. Sightly redundant but I sleep better!
I got all of my cables, terminals, solder slugs, etc from
Quality Copper Battery Cables Made in the USA! - BatteryCablesUSA. Great service and products from my experience.
View attachment 1716315200
Hope it helps!