Chuck,
I have shot both JD338's 35 Whelen and my own 375 Ruger. In my opinion, the recoil on the 375 Ruger is much more than that of 35 Whelen. In fact, I shot my 375 Ruger just 7 times. I found shooting the 375 Ruger to be very unpleasant, and I immediately swapped it off for a BLR chambered...
From a conceptual standpoint, could a bolt-action rifle (such as a LH Win M70) originally chambered in a WSM such as 270 WSM or 300 WSM be successfully re-barrelled to a 6.5 PRC? The WSM cartridges have a rim diameter of .535" whereas the 6.5 PRC has a rim diameter of .532". Is that too much...
Condolences on the loss of your Uncle.
This is a beautiful rifle. That is one amazing piece of wood. Wishing many happy memories while shooting this unique heirloom.