Belt question
 

I recently bought an 87 gt. I had the belt blow off on me and im having problems finding the right size. The car has underdrive pullies and no smog pump. So far the sizes i've tried are 770K6 and up. The 770 fit well but the belts that go around the alternator to the tensioner are touching. Does anyone know the correct size to get so the belts dont touch?

thanks for any help you all can give!

i figured it out, 760K6