Take your stock belt and make a straight line on it with a pencil.
Then wrap your belt around the way tou what it on the pulleys.
tuck the exces belt down.Then run the belt over the mark,and make
a mark that lines up with the first mark.Then take off and measure.
To get some adjustment.You can use a round file to make the alternator bolt
hole bigger.
You will need to remove the alternator bolt to get the new belt on.
I think my belt is 51 inches,but I have under drive pulleys so mine would be
different.
Randy