where to find a smaller crank pulley?
 

What car would have a smaller crank pulley for my 351w?
I'm having trouble keeping belts on th alternator.
Everything seem aligned properly now and I still keep tossing belts. I even use the "good" belts.(gatorbacks)

I was told to use a smaller diameter crank pulley to underdrive the alternator.
I just wanted to know what cars would have a smaller pulley.
Mine measures 8 inches.

I'm not completely familiar with the 351 powered cars, but I would tend to believe that they had the same crank pulley. Does summit list an underdrive dampener for it?