[bushpilot]

I also have an (04) F350 pickup -

in DUEL alternator (ambulance configs) upper/primary alternator is higher output 135 amp vs the lower (backup/secondary) alternator thats rated for 120 amps. On single alternator truck the (only) alternator is 110a.

I replace my single 110a alternator w/ a single 135a - mostly for the electrical load I create and added a 3rd battery on the frame rail (using the e350 Van battery tray).

My point is, you might have the option of using the VAN battery trays to mount batteries to the frame (under the passenger compartment), and using higher output alternators