The only thing that may be less than ideal in opening up a 35 Whelan chamber to 358 NM is that the barrel twist rate may be way to slow for bullets heavier than 225 grain at the velocities being discussed. From memory 1-16 was the original twist rate, this of course could vary depending on who made the gun or if its even the original barrel in the gun. I would check the twist rate of any potential purchase first before buying.

Matt.