bsa: Nice project!
Friends and I built 3-4 pre 64 338's about like yours back in the 80's using Brown Precision stocks and Krieger tubes.Weight was about the same.
I would drill the scope base holes out to 8/40's.. I had seen these rifles chew though the standard screws and snap one off now and then with enough shooting.The 8/40's stood up to the pounding.
My pre 64 270 got hunted yesterday in a nor'easter....it's fine.