I have sent this question on to a 4104 owner that I know.
I think this may depend on the individual coach since the 4104 buses are all unique bus conversions.
Are they both 12v battery banks?
Is one bank of batteries a bank of deep cycle batteries? (if so, those would be the house batteries. You would not use deep cycle batteries to start an engine.)
1977 Argosy 20 Motorhome
1974 Volkswagen Beetle (toad)