I wouldnt alter your pre 64 if it’s in good shape, I have a 1952 Sporter in 30-06 as well and it’s a gem. That said having owned both the whelen and 338-06, my preference is the 338. I had JES punch out a Kimber montana and chop it to 21 inches. It pushes a 205 hammer at 2800 with RL17 easily. I’d find a different donor and build a 338-06 off of that.
