Use whatever rifle you're comfortable with and if it's really heavy cover terrain - then be prepared to track and possibly lose that animal unless you get a cns strike or break both front shoulders.
In heavy brush that goes for miles - I'll sacrifice a couple pounds of meat and take the shoulders out, as opposed to making a great "boiler room" shot and hope for a good blood trail. Snow on the ground makes it a lot easier for tracking but a well constructed bullet in the shoulders normally ends that task.
Dragging anything uphill is a real PITA, as is dragging anything further than you needed to. Quartering or deboning an elk in thick cover is no picnic, so take a little time and talk to your buddy and see what he does, as a 45-70 in the boiler room usually has the same effect as a 300 mag and that is the animal takes off at warp speed and piles up at a later time - sometimes 10 yards away and sometimes a quarter mile or so from where you wanted him to go down.