Alternator issues

so I have a strictly race 64 dart. 496ci engine with a 1 wire 90 amp alternator. Wire from alternator to battery. No disconnect in-between. Not sure what is going on but my alternator's keep going out. They quit charging after only an hour or 2 of total run time. On top of that my batteries are being drained. I am at a loss. Getting tired of buying alternator's. Any help or suggestions are welcomed.