What I'd really like is a gun that has access to both open sights *and* a low power scope.

First choice would be to put an optic on the target. I'd like to have the open sights as a backup....if the scope failed (for whatever reason).

Can one even get/mount a set of scope rings that mount and sit high enough over the sights on a LA 45-70?

I come from the school of one shot, one kill. Don't really need a lever action. Any good bolt action gun would be fine.

Pretty much if I am not 100% sure I can't kill it with one shot, I won't shoot it.