Since it's bouncing around, I would go with some welding cable.

https://www.amazon.com/TEMCo-WC0203-100-Welding-Battery-Copper/dp/B01JMNKUFU/ref=sr\_1\_1?crid=8T2NVW7HWW4O&keywords=welding%2Bcable&qid=1647317751&sprefix=welding%2Bc%2Caps%2C554&sr=8-1&th=1

These are good switches https://www.amazon.com/gp/product/B00445KFZ2/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

Fuse https://www.amazon.com/AUTOHAUX-Gauge-Inline-Holder-System/dp/B07X7MCGW1/ref=sr_1_40?crid=A0UTK6NGEYK&keywords=50+amp+fuse&qid=1647318117&sprefix=50+amp+f%2Caps%2C380&sr=8-40

Terminal kit + hammer crimper. https://www.amazon.com/Battery-Crimping-Terminal-Tubular-Connectors/dp/B0986ZG533/ref=sr_1_13?keywords=hammer+terminal+crimper&qid=1647318253&sprefix=hammer+terminal+%2Caps%2C271&sr=8-13