If it was a mix of parts I would consider hunting down a NOS barrel, but seeing as its mostly original I'm loathe to do so.

I gave the chamber neck a tickle with a .50cal brush with JBs on it in a drill last week, and shot it again today. Got some OK groups, and extraction was easier but not perfect. I'm going to persevere with it a few more times, and if it doesn't get better it'll be sold....