manifolds or headers??
As far as theories?? What do you mean, what size tubing to use on primary's or collector's?
As far as dyno numbers I have seen motors make over 2,000 hp with shorty headers with turbos mounted to them.
Reason guys don't run headers on rear mounted setups is because it has a slower spool time and the truck manifolds hold the heat better which keeps the exhaust velocity higher.
What model year g-body? Like a malibu, gn or monte carlo?

https://ls1tech.com/forums/forced-induction/862310-79-camaro-build-up-6-0-l92-twin-s366-s-build-pics-inside.html
I am using Caddy CTS-V manifolds which should also fit your G-body car because your suspension layout is similar to mine.
Fabricating the turbo plumbing is much easier if you can use cast manifolds as a starting point.
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The 90* mandrel bends are 3" OD pipe with a smooth 4.5" centerline radius,
so I can't imagine they will be much of a restriction at only 12" long.
Here is another pic from a different angle to show that they are actually not tight bends at all.

Custom turbo headers sure are nice looking, but I can think of other ways to spend over $1,000 and/or a few dozen hours of fabrication time.
The Ohio boys and a million others have proven how much power can be had from stock cast manifolds.
If you can find manifolds that will work out for you, I say go for it!
Last edited by camarols1; Feb 12, 2008 at 08:46 PM.
I planned to do that anyways for cosmetic reasons, so it's not a big deal to me.
I am trying to keep an old school look, so it works out ok.
relocate the coils.
I you were to use a GTO or Vette LS2 manifold on the driver side and a CTS-V manifold on the passenger you will not have to relocate the coils.
This is what TOOSLO5 did and it works well.
Here is Dave's setup below.

The 90* mandrel bends are 3" OD pipe with a smooth 4.5" centerline radius,
so I can't imagine they will be much of a restriction at only 12" long.
Here is another pic from a different angle to show that they are actually not tight bends at all.
Custom turbo headers sure are nice looking, but I can think of other ways to spend over $1,000 and/or a few dozen hours of fabrication time.
The Ohio boys and a million others have proven how much power can be had from stock cast manifolds.
If you can find manifolds that will work out for you, I say go for it!
If you use the truck manifold on the DS you have to relocate the coils on the factory bracket a bit. I drilled and tapped holes on three of the four coils slightly higher than the factory location and plug wire issues shold not be a problem.
and then some sleep! 
