First thing, are you sure the NEF Handi will handle the high pressure of the 454 Casull?
As for loading if you buy 45 Colt dies, you can reload for both. I first bought 454 Casull dies and then later purchased a 45 Colt and the Casull dies wouldn’t crimp the shorter case. I fixed it buy using a LEE crimping die.
yooper77