Generation IV Internal Engine - lq6.0 block cnc'ed lsa headed 408 on high boost

OK so I've been posting up alot of different combo questions lately because I have been collecting multiple setups. I was gonna run an ls7 but now I think I'm gonna go iron block so I can run a bigger shot. Also i dont mind a fairely large camshaft but something that isnt gonna be impossible to tune

So here's what I have-
6.0l block yet to be bored
Lunati pro billet rods 6.125"
Lunati pro forged crank 4.00"
LSA heads that are going to wcch for their cnc treatment should flow around 350cfm
Arp head studs
Arp main studs
FAST 102 big mouth throttle body

Still need-
Pistons- any off the shelfs up to the task?
Holley hi ram
Custom cam
Injectors
and lots of little stuff

Now I have some questions-
What kind of pistons would you guys suggest that will handle around 20psi What kind of rpm should I expect this thing to turn
What kind of compression can I get away with on an intercooled e85 setup
Does the block need to have the mains doweled
Is there really a risk of piston rock when using a 4.000" stroke

Sorry for all the questions and thanks for any help- Nick

Couple more things you might need to know...

This is a street car
It will have a t56
Its going in a 3000lb 4 linked and tubbed 65 mustang

So you have all these parts already and ready to be assembled or what?

I have everything I said I have... still need manifold, custom cam, t56, pistons for a 408. I do have pistons for a 427 though.

I'd bore it to ls3 specs (4.065) and use wiseco pistons. This would net you close to 416 cubes.

Just watch as with the 4 inch crank, the pistons tend to rock in the bottom of the bore causing ring seal issues.

Another option to avoid this is look into a 3.9 inch crank. This would net you 405 cubes and make killer torque under boost and keep the pistons stable in the bore.

Car will be on spray no boost and I already have the crank. Hopefully there is no issue

EDIT- car is gonna see boost, decided against the nitrous idea

I'd bore it to ls3 specs (4.065) and use wiseco pistons. This would net you close to 416 cubes.

id watch boring it that much if he is gonna spray.. id prob. stick with a 4.030 bore

4.030 is what ill stick with... not worth it for ten cubes

id watch boring it that much if he is gonna spray.. id prob. stick with a 4.030 bore

I was looking for ease of piston avaliabilty. seems more variants of pistons are avaliable for standard LS3 bore.

I was looking for ease of piston avaliabilty. seems more variants of pistons are avaliable for standard LS3 bore.

True but it's not like he's using an oddball bore size. There are plenty of 4.030 shelf pistons available, including wiseco.

I'd use Diamond pistons if you are going with the big nitrous shots

Do you guys see any problems with the 4.000" stroke???

Do you guys see any problems with the 4.000" stroke???

Problem no.

But you won't have the long life and reliability of a shorter stroke engine.

if i can get 15-20k miles out of it, id be just fine

what kind of pistons wold you guys suggest for this build?

Any quality 2618 alloy piston. Get them coated on the sides if you can. Wiseco, Diamond, JE etc.