Your not following what I am saying. You want your cranking battery as close to your starter as possible. And Chris is right. Get the vehicle up to par and if the battery doesnt fit right, get the right oe fit battery first and THEN wire a second battery back there.
Or, you can ignore all that we've been trying to tell you and just do what you want but that alone may not take care of your issues. On a diesel, cranking power is not the only thing you need to worry about.
