A step by step on how to replace your welding ground lead and some info you might need when selecting materials.
EWCS 4 guage wire
https://www.amazon.com/gp/product/B01D0ZOL42/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
400amp Brass Ground Clamp
https://www.amazon.com/gp/product/B002ACOXM2/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1