Listen, here's the deal. A number of people have come in here all excited over the years, just like you that they WERE going to build a twin turbo contour/cougar, and it was going to be badass. EVERY SINGLE ONE has fizzled out and disappeared, and none has ever been built. There is usually at least one per year, sometimes more. Sometimes they are newbies, and sometimes they are well respected members of the site. And again, EVERY SINGLE ONE has fizzled out and never happened.
Now, if you really can get cheap engines/parts from AER, that is fantastic, and more power to you (no pun intended, ok maybe it was) Didn't a remember you saying you worked there or something anyway? AER does a LOT of regular engine rebuilding, I know they get a lot of OEM service valves from my company for a number of engines.
And finally, on your plans. I really think you need to revisit everything from the ground up before spending too much cash. Recheck everything you think you know about single turbos vs. twin turbos. Really think about what benefits you want out of a twin that you really won't get from a single, and whether the cost benefit is there. (Hint, while a smaller turbo may spool faster, remember that only HALF the exhaust energy goes to each smaller turbo . . .) Further, if quick spool and good low rpm performance are really that important to you, consider raising the CR back up some, and lowering the planned boost pressure. This would give better off boost performance, and spool the turbo(s) more quickly too.
You have to keep in mind here, that a number of the guys giving you advice in this thread are either engineers that design engines and engine parts for thier day job, or people that have built thier own forced induction duratec setup already and gone through all the same stuff you are trying to figure out right now.
