It's called JP Carroll's, in Lexington, MA. It's a junk yard but they have a guy that specializes in radiators. I would check to make sure he's still there first.
Anyway, yes they did a triple core for my old Jag and that car never overheats despite not having the common add-on electric fan. They got one that wasn't too thick (eg fit nicely), and straighted up my top/bottom tank as well. The only thing they did that I did not prefer was they put in new filler. I would have preferred to keep the original Jag filler neck assembly. But they did remember to keep and return it too me.
They've also done a couple cellular cores for old Jags that are period correct (concours competitors). Nobody I know has any complaints with them.