383 appearing, 400 stroker with stealth heads question.

To put into perspective how bad the stock low deck 4bbl manifold is…….

I dyno tested two BBM strokers on consecutive days.
One was a low deck 511, the other a 499 RB.
The 511 used the factory 301 manifold with some work done to it, the 499 had a 6bbl.
Both were run with the same set of B body manifolds.
Both were 12:1, and running SR cams.
They both had ported 906’s, and the heads on the 511 were a few cfm better.
Both cams utilized the same intake lobe and lsa.
The 499 had a slightly faster ex lobe.

The difference in power was about 65hp.

If you’re “trying to make power”, the stock low deck intake manifolds are a pretty big hurdle to overcome.

I later got to test a different low deck 511, which was an overall much higher effort(and $$$) build.
That engine had an extremely modified 301 intake, 14:1+cr, and an .800 lift cam.
It made slightly less hp than the above referenced 499-6, which was a very basic straightforward “bread and butter” build.
From what I understood, this high effort 511 was about 3X the cost of the 511 referenced above.

The bottom line is, you’re not going to get 500hp on a legit dyno from a low deck pump gas stroker street/strip type combo using a factory intake and ex manifolds, unless the intake has had quite a bit of work done to it(and it still won’t be as good as an ootb rpm).
And even then you’ll need to be running all the CR you dare, and not a “small” cam.

Do yourself a favor…….use a good intake manifold.

Edit- I re-read the OP.
Go with the RPM(or a decent single plane) and the headers.
Then the power potential would more be dictated by the level of work done to the heads and how much cam you can tolerate.