I have a 64 Polara with a big block and a clutch fan. Been so long since I put it in I don't remember where I got it. Pretty sure it's some kind of Mopar clutch, though.
I did have to melt the solder holding the brackets to the radiator and move the radiator forward, then re-solder. But I think that was because the radiator shop that put a new core in didn't put the brackets back in quite the right spot.