Many pitted barrels can be very well salvaged by lead lapping & fire lapping even in extreme cases. We've done a few with excellent results. Firelapped barrels I've done have shot extremely well with black powder loads as long as a black powder lube was used like SPG or Lyman's Black Powder Gold. Excessive fouling did not happen. .457/8 cal. has many bore-riding style bullets (long noses) that do an impressive job of lapping the lands as well as the grooves. Saving the original along with it's stampings is well worth the attempt.

If re-barreling, I'd go for a shorter, 2.4" to 2.875" case with faster than normal twist - ie: 18" for heavy bullets. It would then become a long range rifle.