If you can still find a radiator shop where somebody remembers what a torch and solder looks like, it's pretty amazing what they can do. Fan arc damage to the core usually covers several tubes, and the only effective repair is to pinch off the damaged tubes top and bottom and solder them shut. This reduces the cooling capacity in direct proportion to how many tubes you have to disable.

If the damage is on one of the tanks or the header, it's possible to do some patching, but there are places that get damaged where there's nothing to do but do a recore. I'm just old school enough to absolutely refuse to use JB weld- - - - -fix it right or replace it.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!