The answer to your question totally depends on the condition of the particular receiver that you bought.
The mauser 98 action, in general, is among one of the strongest designs in the world. However, consider the following factors:
1. The K-98, as with almost all military mausers, were not made of high grade nickle steel (as are current guns). They were made with carbon steel, which was generally okay for the type of round that they were designed to shoot. These receivers, however, are now more than 60 years old.
2. The K-98 was designed and manufactured specifically to shoot the 8mm Mauser, which has a chamber pressure in the area of 50,000 psi. Check the manuals on the two rounds you are considering. They may, even in factory loads, generate standard pressures of 65,000 psi or greater! The .308 Winchester, and .243 Winchester, are both in this category. Since the .358 Winchester is just a necked-up .308 Winchester, I imagine that it would be in this neighborhood as well.
3. Many many K-98s made during heavy wartime (1942 to 1945) were made by slave labor, in factories that were being bombed. When and where was yours made??
4. The best K-98s were made pre-war, during the years of 1938, 1939, 1940. Even these, however, could be stressed out or unsuitable due to abuse, rust, etc.
5. If you have a high quality pre-war K-98, then the last thing you want to do is to destroy its collectors value by re-barreling it.
The only way to answer your question is to have a qualified gunsmith, who is very experienced in custom mausers, examine your action. I would also suggest that you have it tested by the magna-flux method, to make sure that there are no small cracks.
If your receiver is covered with rust or pitted, then I would not go to the considerable time, trouble or risk of rebarrelling it.