Millenium is a good place to get cylinders replated. Contact Hardass here on snowest. He has connectons with them and has always been able to get me a good deal. I have used SPI pistons with good success, oem ones have been good too.
One trouble with the big block cat engines is the carb models mix the oil into the fuel pump. If you plug a jet or otherwise starve it for fuel you also starve it for oil and they don't run very long without oil. If you have one that seems to be running on just one cylinder better shut it down and find out why and not try to limp it back to the trailer.