Hi Jim,
You can get the clevo heads on ebay, they're about $1250 Australian over here.
Here is a flow test done on a casting. The same forum is buying a set of heads to bolt on to a 351C and see how they compare to a set of 2V's. Have a search for the other posts on the same forum.
http://www.fordforums.com.au/showthread.php?t=87997
Judging by the pics and flow numbers they really need a clean up before use. Looks like they need a filled manifold to match the intake ports properly too.
Darren