[GCMustang]

Actually, I'm not sure exactly why they don't fit. That is actually just hearsay, so check with March or Steeda. But I'm pretty sure the March pulleys are stamped steel bolt ons, and since the Steeda timing adjuster bolts on to the damper, there would not be enough clearance. Double check on that, though.

Yes, though, a chip is actually a better way of adjusting timing. Setting the base timing using a Steeda T/A is a good way to pick up some hp, but especially with non - nat/asp cars, a chip is a better way to go.