It sounds like a loose ground connection. Check ALL of your connections to the batteries and the starting solenoid. Check that they are CLEAN and tight.
It sounds like you have an ambulance with dual alternators. No need for dual alternators, so go with the 200 amp alternator. 200 amps is a LOT of current!
I sold my 2004 F-350 about 7 years ago. I did not need that big of a truck. I bought a Toyota p/u and kept it for two years and got rid of it. I just don't need trucks any more and if I do I can rent one...
Smog laws differ in each state. California has the toughest laws in the Nation. We pay a lot to keep our trucks registered here. A truck that you buy in Idaho, for example, can not be registered in California. BE CAREFUL!