With only marginal gunsmith knowledge this is what I believe.

No change in the boltface.

Since the 30-06 is a full length long action round and the 7x57 is somewhere between a short action round and a long action round there may be some mods required, possibly a mag box filler.

The profile of a 7mm case is different than an -06 case and thus would have some minor changes in mag box config to get it to feed.

If given the choices I agree with going to a .280 Rem. but if that is your only choice I wouldn't do it.

There may be a good reason why a 7x57 barrel is available.