Who makes the Downs Ford pulley?
They are not all the same. Some are much more aggressive in their design and will eat a belt in no time. Others are not finished properly and do much damage to the belt.
The Gates green stripe is probably the one used most sucessfully with the cross cut pulleys. The Gatorback belts can end up chewing themselves up because of the type of contact between the teeth on the pulley and the teeth on the belt.
If a regular Gates belt doesn't fix it, start looking for alignment issues.
Dan