Nick's Garage dyno's a 318 Stroker.

from prior discussion and dyno results, the threshold for manifolds and shorty headers is about 400 before they start becoming detrimental to power.

however, headers will pick up some torque over them in the low and midrange.

but this thing doesn't seem that wild, and with the manifolds and smallish carb i'd bet it's super crisp on the street and has great throttle response.