General rule is that any solid fixed ring/base system will probably need to be lapped when mounted on a factory mass produced receiver. That said, if you bed the scope base to the receiver this will help a great deal and at times eliminate this need totally depending on how out of true the receiver is to begin with.
As far as torquing the receiver screws, the stock is pillar bedded so you can snug them down to the full 65 in/lbs if you want. With a properly bedded rifle you will generally not see alot of difference between 45 and 65 in/lbs of torque. Being as you have a heavy barrel with a muzzle brake and in a high intensity round, I would go to the 55 in/lb range at least to be on the safe side.
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.