I just used a 3.5" to 4" adaptor for mine. I had 3" into the intercooler and 3.5" out.

 

If you're really trying to make big power (1000+) I would go as big as possible on the cold side. Mine was 3" all the way, I don't think it hindered power but I do think it led to higher IATs than a 4" pipe would

 

I may step it straight out the cooler to 3.5" then 1/2 or 2/3 up step to 4"
As usual im going to push it kinda hard and get whats possible without just throwing the bank at it

 

How much power are you looking to make? Be realistic.

The cast 480 will make 1000 rwhp on a 370 but it will be maxxed out

 

Honestly i would be happy with 800. But im looking to try to get down into the 9's in the quarter, so whatever that takes to get there.
My problem is the fuel. I dont know where the closest E85 station is to me. Im thinking its about 2hrs from me

 

That's not really realistic for e85 then since youll get around 7-8 mpg. Unless you can barrel it.

Stuff is great for boost though.

 

Yea I can get it for sure 55 gal at a time since I've got a friend that works down there quite a bit and is home on the weekends. I've heard of one local place that supposedly may sell it but I need to go check and check with some other local suppliers about getting it.

 

Really though at what point is E85 critical for use?
I was planning to run CR with the motor build under 9.5 :1

 

No need for a 4" tbody pipe.
Throttle body isn't that large. Unless you have a 102 and that still isn't 4" when you count the throttle shaft and butterfly in the way.
3.5" pipe is easier to fit turn radius and all.
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Down pipe 5" is over kill.

 

Well I know I have lots to learn obviously but I have time because I am about to start the build on my shop so I can take my time and work on it at will and not having to drive back and forth to my dads shop and take up his space he uses to make a living.
Now back to the build.....
At minimum ill run the 3.5" but I plan to step it.