Hmmm. Did you degree the cam? google 460 timing chain marks and you will probably learn a lot. Carb choice has a lot to do with things as well. Have the heads been ported an polished? Those can get screwed up in a hurry if the wrong things are done to them.
Distributor could be 180 degrees off, but I'm not sure that those motors will even run that way.
I'm running a smaller cam than you listed and mine idles above 1000 RPM just to stay running and I'm pushing 35 degrees timing. That will probably get backed off a touch as the rings seat and compression is increased, but that's 1 more thing for you to check.