Something to keep in mind if you are getting a reciever type scope mount is that your rifle has a removable barrel. If you mount your scope to the reciever and then remove your barrel to clean it you will most likely change the point of impact causing you to have to sight in again. You might get lucky and it will stay the same though. I would not hunt with it without shooting it first to make sure everything is still on though.

If you want an accurate slug gun you normally either need a barrel mounted scope or have your barrel pinned to the reciever. My suggestion would be to get a barrel with the cantilever scope mount.

As far as not being able to take the shot because of the range, well that is why it's called "hunting" not target shooting. I admire your dad for knowing his limits and not taking a "hail marry" shot at it anyway regardless of it's size. Many hunters would have tried it. Some peoples ethics drop the bigger the rack gets.

Paul