500 horse w/ cast heads??

[71runner]

been looking around at proven engine combo's for awhile, tons of good info on this board, but alot of the combo's ive seen are running aluminum heads. i found one combo over at moparts pushn 500 hp 510 tq with cast heads and i was wondering if i could get some guidance from some of you guys on a build?

heres the build from moparts: http://www.moparts.org/Tech/Archive/bb/4.html
its pretty vague, 9.9 cr, 292 cam, 850 holley, torker II, and ported 346's w/ big valves flowing roughly 260cfm

at the moment i dont have any aftermarket parts for my build, trying to get everything figured out before i spend any money

heres what i have: 77 440 motor complete, cast crank will go away (getting a steel  one from a friend) and the rest will probably go in the trash
the heads i have are 906 castings, .060 milled off 2.14 1.81 valves, 3 angel job with back cut valves. bowl ported with mp templates by previous owner and he was running 11.60s in a 66 belvedere with these on a 440 (or so im told) and from what ive gathered by looking around my best guess would be they flow somewhere in the 250 cfm range at .550 lift. this is what i used as a comparison: http://www.moparts.org/Tech/Archive/bb/40.html

the intake i was planning to use was the holley SD topped off with an 850 dp

i was also looking at the thorley 1 3/4 headers (unless a 1 7/8 tube would be better suited for this build? )

from your guys experience, would i be getting enough air flow out of that combo to support 500hp/tq or would i have to bite the bullet and got with a set of eddy's? (aluminum heads on an e3 budget hurts)

any help would be greatly appreciated!