Nick's Garage dyno's a 318 Stroker.

junkyardhero said
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.

Bet you that thing does run crisp on the street. Considering it has a dual plane manifold and assuming the divider is not cut down, each cylinder only sees 375 cfm. A big prepared thermoquad would be an excellent choice carburetor. Those manifolds have to go, fenderwell headers if you can find a pair.