i have a pair of these:
http://cgi.ebay.com/ebaymotors/SBC-C...item2c56e1a78a


well, my gta had twins on it back in 1990 up until 2002 or so when i bought it. i have fancied the idea of getting that setup back on there, so i bought the cast manifolds to get started. the car absolutely hauls ***** on nitrous, though so its been a tough decision for me to go away from it. anyways, im looking to make somewhere around 1000rwhp thru a th400. engine will be a 358" at first, and later swapped to a 400-420"-ish. will probably be turning 7500ish rpms. air/water intercooler will be used.
my thoughts right now are a pair of ~70mm turbo's, but not really sure what i should shoot for on the a/r and stuff like that.

any suggestions on sizing or brand/dealers etc. would be great. or, should i just sell these things and do a big single?

 

Those manifolds going to fit in the thirdgen chassis? Driver side may sit right on the brake booster/master cylinder, and even if it clears, where to route the down pipe?

For twins with 1000whp, 70mm turbos should do it. Brand is up to you. 70 mm stuff can make 1200-1400 on motor which is plenty for 1000whp.

What rpm range you looking for? For a 358, i'd go for 6400 rpm peak hp. Puts you around 24-25 psi for 1000whp. need around 60-65 lbs/min air flow per compressor with a pressure ratio of 2.7. That will put you in a good spot on most 70mm turbos like garrett gt4294.

For a single, guys have done well with 88mm-91mm stuff. Depends on how you want to package it all in the engine bay. T4 70mm stuff aint that big but a T6 88 can be huge. Twins you can run 2 smaller 3" downpipes as opposed to a big singles 4-5" pipe.

 

these manifolds are pretty much a knockoff of the gale banks manifolds, which is what was on the car before i got it. they look like they would fit pretty good, but one thing i remember is the gale banks setup used center inlet housings. im assuming to move the one turbo off of the valve cover?
i also just checked out a very nice set of headers from stainlessworks that supposedly fit thirdgens. hmmmmmm......

here is a pic of the car before i bought it-
[IMG][/IMG]

 

stainless works looks very nice but are pricey. There was a guy on turboforums making headers for s10's and other sbc's that may fit a thirdgen well for like 650 bucks.

Hanging T4's out in front of the motor and have downpipes curl under the manifolds or somewhere under the kmember...tubular helps here.

 

I just bought the same ones a month ago. I'm planning on using MPT62's with my set up though. Can you post your progress with the manifolds? I'm pretty sure you'll have yours together before I will.