Did you try any tuning? Adjustments such as ignition timing and carburetor (Fuel/Air Ratio) can make a big difference in power. On my hemi, adjustments to timing and changing jets in the carburetor helped me get 80+ more horsepower on the dyno. Not sure if you could see that much, but if you just have a bunch of parts bolted together, tuning would almost certainty help you find some hidden power.