The standard belts available do seem to ride high in the groove in the alternator pulley.

Our 69 Dart 383 GTS has a tendency to spin those off.

The belt that sits deeper in the groove is a DAYCO Top Cog belt.
It doesn't spit them off at the track.

It's not a correct looking belt though if you want a factory looking belt.
Many belts have what look like teeth (cogs) on the inside of the belt, on the Top Cog those are on the outside.