Some other ideas i see on others forums are . if you do not want to buy new belts then remove and clean the belts you have , so they are not smooth and shinny , then reverse the belts when you put them back on .
i have an old car with an inline Ford six engine , so ideas i see on the ford six engine forum is use hairspray on the belts , some members on the ford six forum also say a 60 amp alternator is the maximum amount of amp output we can ask for a single V belt . So on my car with the inline ford six i reduced the alternator to a 60 amp alternator , i had a 70 amp alternator , so reducing the alternator amp out put by 10 amps , fixed the belt squeal issue on my in line ford six .
So then if a 60 amp alternator is the max a ford six engine should have with a single V belt , on the ford inline six the belt goes around the water pump And Crank pulley ! Then what is the max alternator amp out put for a 307 engine that the alternator belt Only goes around the water pump pulley ?
some inline ford six owners double up the V belt on the alternator, so 2 belts going around the Crank pulley and alternator !