The 30-06 definitely has the edge for versatility, but for what you asked, I'd lean in the direction of the Marlin in .45-70. While the BAR, if you take care of it, should be reliable in all but the most extreme circumstances, the lever action will still edge out reliability wise. And since you specifically said you'd be stalking, it's reasonable to conclude that ranges would be short enough that the trajectory advantage of the -06 wouldn't be all that important. Also, for stalking, a short, quick handling rifle like the guide gun with iron sights (I'd go with a ghost ring, myself) will edge out over a scoped BAR should you jump one up close.

Mike