"shoots all over the place"......
What loads ? Very possibly your 98 just doesn't like the loads you're using.
The Germans did not use corrosive primers, at least not by the time the K98k came around. So, it is unlikely that your K98 has a pitted bore. Could be shot out.....the crown might be damaged, the stock to action fit may be bad, etc. etc. Lots of things to consider before a re-barrel.
To the OP:
A great many surplus Mausers do not have "sharp" or "crisp" rifling. However, with the right loads, etc., most can be made to shoot well. My Yugo M48, which I re-barreled using an unused, spare military barrel (essentially a brand new 50-plus year old barrel), did not look as sharp or crisp as modern commercial rifling does. Regardless, it is quite accurate.
IMO, the most important things to look for as regards the barrel are A) that the barrel has no pitting and B) that the crown is in good shape. No question, surplus military rifles are always a roll of the dice, so to speak. But, if you are prepared to put enough effort into it, they usually can be made to shoot as well as one could expect - given what they are.