Here is an interesting little link to the Edelbrock Foundry's website. Seems to be more of sales tool for their foundry services but there are some pics of cores and stuff and a video that shows some heads and manifolds being made. http://www.edelbrockfoundry.com
Years ago Vic, jr tried to produce in Mexico. The quality was damn near impossible to control, so he built the state of the art factory shown in that clip right here in the USA.
I've not been to the foundry but I was lucky enough to get a tour of the edelbrock factory building(s) in Torrance, see http://www.flickr.com/photos/hotrods/sets/72157603836886364/ The volume of stuff was crazy, I think they said there were 3 deliveries a week of rough castings to the factory - intakes, heads etc.
THAT was cool! Wow. Too bad I didn't see that when I was writing my paper on sand casting cylinder blocks for my manufacturing processes class.