Farshot:
Without having to work the bolt face and rails over a bit, the easiest rebarrelings will be off your current .532 case head/.513 base -- such as 450 Ackley, 450 Canadian,458 Lott, 470 Capstick or 475 Ackley, etc.

As to reboring, depends on the barrel diameter, metallurgy, etc; had Labounty rebore for me in the past with great results, Cliff retired and sold to Clearwater. (deltagunshop.com)

Or ,try Randy's, Redman's or Classic(though , I have not personally used them, but I have seen good work from all three )

If you wish to open the bolt face, widen and reshape the rails, fiddle with the magazine and perhaps open the action itself up a bit you have numerous other choices off several parent cases.

All depends on how much time and money you wish to consume.