The problem is only partly the 1/2” belt, the other half is the load you are placing on an alternator not designed nor intended for that type of demand. Your bank is grossly oversized for your stock alternator to cope with, without issues..really if you have problem like mine watever belt you are using is the same, i had every brand in my engine.
Rx:
Serpentine Kit
Performance small frame alternator - eg: Balmar 6-series
Balmar MC-614 regulator & alt temp sensor
Set belt load manager to level 4 or greater