If it doesn't come up to your expectaions the first thing I would check is your ignition curve, Stroker BBM's with street compression ratios tend to like a fair amount of initial timing combined with a limited/shortened centrifugal advance that's all in by around 2600-2800, timing can make a huge difference in performance. Several Times I've seen guys who never really built strokers before get them running with 10-12 degrees and they start and idle "fine" but the power and torque just isn't there when they drive them....Fix the timing and "BAM"! instant stroker happiness.

Back before we had all the closed chamber head choices Diamond and I think KB used to sell pistons with a "qunch step" so technically is had a flat dome that would take up a good portion of the open chamber. I built a really nice running 508" RB with some well ported Stage V's that ran really strong with a mild Hydraulic roller. That beast is still out there somewhere, I need to check with Paul PHJ426 to see where it's at.

Was there any work at all done to the heads? With strokers picking up the mid lift flows (particularly the .250-.450 numbers) really helps the torque and HP curve above the torque peak. As I remember the OOTB edelbrocks aren't really "killer" at .400 lift but they are easy to improve with skilled bowl/runner work like you can get from Dwayne Porter. just getting from 260 cfm to 280 at ~.450 lift will really wake up a strokers power curve. And combined with a better/more consistent (than delivered OOTB) valve job helps the snap and response and can act like a bit more agressive cam profile with no downside.

The pistons are obviously not going to help you (just something for readers to keep in mind) but possibly swapping your heads for a closed chamber like these new TF 240's and either port the RPM or swap it for a Holley Street Dominator with a little port and mainly plenum work would likely help out immensely. A custom calibrated 950HP or 1000HP 4150 base carb would help the breathing up top, as said with a dual plane each bank is effectivly limited to seeing only 1/2 the carb so the combination of a small runner/port with a small-ish carb puts restrictions in series which makes matters worse.

See where your curve is first, try running something like 16-20 degrees initial and limiting total (initial plus centrifugal) advance to 34-36, I'll bet that will make a difference. On paper your motor should run strong.