Which caliber Ruger #1 would be the easiest and most cost effective way to convert to 450 Nitro Express?

I think the chamber on a .458 will clean up, but not sure. You could use the 45-70, but then you are looking at a very light weight 450.

If you're interested there's a fellow here in ABQ who's selling a #1 already converted to .470 NE and deal includes dies and ammo. I should be able to get a name/number.