Since the 358 is simply a 308 necked up to 35 caliber the conversion would be quite easy. A simple rebarrel or rebore. Though I don't believe the gain would be worthwhile. I'd simply alter the load. A switch to a 180 grain round nose bullet will give a lot more thuimp. Perhaps the 150 grain nosler partition.,. My hunting buddy loves his 308. I load the Winchester PoerPoint bullet in a 150 grain weight and he kills whatever walks by...