Thanks for the replies... some more questions:

Your cheapest bet for good casting material is to use sand-cast
aluminum scrap such as cylinder heads, transmission housings,
differential housings, etc. of OLDER cars where these were indeed
sand-cast.

What's a good source for this kind of Al? A neighboring garage
is willing to let me take the occasional Al wheel, are those any
good?

What are degassing tablets?

Thanks Roy for the info, nice site too! The shaper's very
impressive. What kind of lathe and milling machine do you
have?

Mike, if you're near Boston we can have a casting party
to get you started with casting while you build the foundry...
I won't do your pattern and sandwork, but will gladly pour. :-)

Tom.
http://www.TomEberhard.com