Don't use Anderson connectors. The SB50 and SB350 styles don't seal and if wet will short out and burn up. The connectors used for long welding cables or outdoor power supplies with the tapered rubber boots work well. Cam-Lok, I think.
After some googling, I found an online retailer (http://www.lightsonretail.com) who carried Cam-Lock style connectors which would work with 4/0 welding cable. These are rated for 400A at 600VDC, so should work well for the 312V Jeep. They are waterproof, interlocking, and very large.
On the left are the components for the female connector; on the right, the male:
This picture shows how the components interconnect:
And this picture shows the female connector with the cam component inserted:
I got enough of the connectors to isolate each major battery group so that I can work on lower voltages than 312V. I found 144V to be dangerous enough; I don't want to work directly on higher voltages if it can be avoided. Which it can by making each battery pack independently connect into the series with these Cam-Lok connectors.