Knocking 340

My engine rebuilder had a dyno. I paid him the extra $500 to dyno it just to erase any future questions about it's horsepower. Glad I did. The other benefit is that it is now broken in, the timing is set, carb is good. Just install in car and fire it up.
As you most likely found out there is a big difference between tuning for the dyno and tuning for the street or track.