Hi, I have the exact model you have. I'm not the original owner so I'm not sure if the 6v battery configuration is factory or not. I've attached 2 pictures - the house battery configuration (6V Interstate batteries) and the truck battery setup. If you are having a specific issue, let me know and I will try to help.
On the house batteries, the red 2 gauge wires are for inverters that were installed.
2008 Gulfstream SuperNova 6372