Replacing negative battery terminal cable

For my sweet old Toyota, a 2004 v8 4.7L, close to 200k miles, which I acquired at 187k, the negative battery terminal cable with engine and body grounds needs to be replaced. Its old and stiff inches from the battery. Its likely the from the original build from manufacturer, never replaced.
As I roughly understand, the negative (ground) cable runs from the battery terminal to the engine block and then through the firewall to the body.
I'm trying to find out what length(s) of cable(s) I need. I could take out the old to find out details, but hoping to have the replacement negative cable(s) in hand when I swap out.

 

I recently replaced mine with a spare 1gauge (1 AWG) cable I had. Pretty straightforward. I cut it off as low as I could go into the OEM loom and just unbolted it down on the block (below the DS exhaust manifold) and cut off what I could. Plan to open the loom right up and clean it up soon maybe replace the positive as well.

Nothing goes through the firewall but there is a body ground to the inside of the DS fender that comes off the - terminal clamp. I used a 6’ and there was some extra.