Well all I know is this thread got back to what I was hoping it would be in the first place so whatever happened seems to have worked.
From what I have learned, it seems to be down to these heads, in more or less descending order. All will require significant port work and parts to get really high flows (300+ cfm).
Eddie Victors
W8 (although I'm unsure about technical challenges of W8, with regard to lifter angles)
W2s
Bloomer
Trick flows
Indy or W5s seem to have a real history with casting problems so that would make me concerned about going that route. Seems risky.