I agree with Ron - The Lee bullet will likely work as well as anything, and the moulds are cheap if you don't like it. The .458 is kind of less than optimal for cast bullets due to the taper all the way to the case mouth, but it'll work OK if you're careful about flaring the mouth and setting the seating die. Cast the bullets hard, use Hornady gaschecks and good lube, and it'll run up to full .458 speeds with no problem though you'll likely get better accuracy a little below that. For fun cast bullet loads, just call it a 45-90 and use the data for that if you don't need full power. Oh, make sure you clean every bit of copper out of your bore first or you won't get very good results with any cast bullets.