If I were to scope a .450, I'd probably mount a Leupold 1X-4X.
Unless you're shooting 1" spots at 300yds, you can see well enough to shoot something as small as a groundhog, and for shorter ranges have a big field of view. I have one on a Rem 870, that gets used for crop damage deer control shooting. It has held up well.
Recoil, get a Decelerator from Pachmyar. Takes the bite out of things like lightweight .375's.