Ford has them listed under two part numbers. Being the cheap #$@# they are, they wouldn't have different part numbers if they weren't actually different. I'm looking to buy a stock Cobra crank pulley, the crank pulley from my Cobra project is gone (shattered in the accident). So I'm trying to find one. Ford has discontinued it (no surprise there). I've PM'd someone off the Corral for one, but no luck so far.
Eddie, if you're right that means the Cobra crank pulley rotates the accessories about 10% slower than the GT. That definitely saves something, but it's not as much as your average underdrive pulley set, which is around 20-25%. Interesting.