So if I wanted to go the twin turbo route and run equal sized parallel turbos, they would have to be small,(right)? What size would you recomend for this type of setup? For a responsive daily driver.

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Go for it, You live this life only once.

The best info I have ever recieved on sizing a turbo came from a turbo manufacturer, or I should say, their local distributor. They were very freindly and helpfull and once I gave them as much engine info as I could give them they gave me a size, trim, etc. I don't have the info here at the shop, it's at home. If I think of it I will grab it tommorow and pass it along. Your engine combo may be completely different (my goal is 10:1 static compression ratio and as much boost as it will handle. I am running E85) so you should give them YOUR specs and goals and let them size it for you.

I like your idea of a twin turbo but after mocking up a couple things in my engine bay I would worry about space and heat.

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Chris'
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Having been around enough turbo engines and working with several combinations of my own I can offer this. Contact a real engineer about the turbo selection and tell them exactly what you are trying to do. The more I have learned, the less I know. I would try Limit Engineering. I can dig up the number if anyone is really serious about a new custom turbo. He has very good prices too.

Otherwise choosing a stock turbo from another application, trying to match displacement, rpm range and boost, can be a good starting point. Possibly very inexpensive too. Having worked with Buick GNs extensively, I think even the stock turbo is a bit much for most slants. It is sized to run at about 13 - 14 psi on decent breathing 3.8 litre engine. Probably good for a serious buildup with EFI if thats your planned boost range, and real easy to get cheap.

Avoid the idea that a turbo that will support huge amounts of horsepower on a 9 or 10 second car will be at all correct for a 200-300 or even a 400 horsepower buildup. It will be a very expensive pig. You don't just get a 5, 6 or 700 horsepower turbo and end up with that. Or just turn the boost down until your setup is ready for more. CFM at a certain boost level is just one of the factors aside from PSI. There is quite a bit more to to it.

You do not need much of a cam either. I would not even try running more than 210 degrees @.050", you simply don't need it to make up to about 350 horsepower @ 15 lbs of boost. . The stock 225 cam would be ok and the mopar 4120243 or the new Dutra / Erson version would be great. Maybe even with 107 lobe centers on the Erson cam. More will just cause lag, kill the power band and need a real high stall converter. You need exhaust pressure to drive the turbo with polluting the charge, hence the smaller cam. Get the most flow you can out of your head. Use the shortest and cleanest header/exhaust manifold setup you can fit. Use a very free flowing exhaust and at least a 2.5" downpipe from the turbo on with an engine this size. Intercoolers are very important but so is the plumbing. It needs to be big enough and have very smooth bends and transitions and be as short as possible or it may be a wash.

A true 7.5 to 8-1 compression ratio is a good place to start for a street engine.