Belt sizes

Rock auto is your friend! don't have to buy from them but it gets you in the right direction. I just chose 74 dart with 360 as a wild *** guess

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ULTIMATELY you will need to find one that fits. and easy way to get in the ball park is to take a length of cord and go-around the pulleys. mark where the two ends meet and measure. if your cord is skinny add an inch or so . If it is 1/2 inch it will be pretty close. then when you look at the belt that is recommended on rock auto you can compare whet you measured and what they offer..

keep the alternator in about mid to 1/3 out adjustment location when measuring

also look at the inside width of the pulleys, your belt should not be too wide it should sit in the pulleys about flush with the outer dia maybe a tad inside.