About the 338 vs 375, recoil is the same but the 375 is much more versatile. I would get your son the .375. John Bolliger and Ray Branigan turn out great custom .375's based on model 70's. My personal preference would be a takedown .375 on a Granite Mountain action with Smithson QD mounts, all by Joe Smithson. I would estimate about 20K for the project. But lots of guys in the American Custom Gunmakers Guild can turn out a fabulous .375 if given a reasonable budget and 2 years.