Morten , since the rifle has already been rebored, there is little collector value anyway, so why not re-barrel it to something like 375H&H flanged, or the old stand by 450/400NE 3". The chamber pressures in 308 Win (7.62 NATO) are far higher than either of the two alternitives. If the chambering will clean out the old chamber, the 300 flanged mag would be a choice as well, but pressures are getting high for such an old rifle, as it is with the 308.
I have an idea the reason this rifle was rebored, and re-chambered to 308 is, it was for a someone who had access to thousands of rounds of 308 military ammo,while stationed in a place, like in RSA,where there was good plains game hunting. May have been done durring the sanctions on RSA, when lots of ammo was hard to come by.

The 308 would be my last choice otherwise!