This 98 you have is sounding more and more like a gun that wouldn' t make a great " piece of history" anyway. If you want a great piece of history, shop around for a decent Mauser in original configuration and in good shape. You should be able to find a decent one for $125 or less and a fantastic one for $250 or less............considerably less that restoring the one you have.

If you consider having your .243 Mauser reamed to another caliber (like Rem 244 or 243 Rockchucker) shop for somebody that has the reamer for the cartridge you want to convert to. A smith may be able to do a great job reaming to what you want, but if he has to rent the reamer he will pass the cost on to you. If you are a member of a shooting club a member may have the reamers and lend them to you if he knows the smith you plan to use.