Bob, if you go the rebore route & I for one think that is a good idea, you need to go at least a 60 mm cartidge length to clean up or reuse the existing chamber as I'm sure you've probably worked out. I like the idea of a 318/338 WR as Naki hunter has proposed, but if the pitting is really bad,a 35 Whelen or even the 9.3 x 62 suggest themselves as attractive alternatives. Of course if you didn't mind playing with a wildcat & wanted to keep it "Metric" then a 9x60 would be feasible, just a lick with a neck throat reamer after reboring & away you go. Not sure if there ever was such a caliber but it would be a easy wildcat to live with brass & projectile wise.
Steve.