Good day

I have a short action center feed Stevens 200 chambered in 308. I would like to know what would be involved in convert to a 338 RCM or a 350 remington mag. I am going on a pig hunt in 8 months and would like to make a dual purpose pig/bear gun. I was also looking at the 358 winchester which I think would be the simplest conversion but it seems to be a bit slow compared to the other 2. I have converted other savages but nothing where I had to modify the bolt or possibly the magazine

Thanks