I had my radiator re-cored for about $220 by a guy in Fremont, CA. He did a good job, and I'm sure you can find the skill at various places around the country.
Unfortunately, I lost track of the guy that was rebuilding a P-51D radiator during my last re-core in 1988, or I would have used him:-)
They can usually re-core them if the top and bottom tanks are in good shape.