With my 383 NOT using the special build crank, but just a 400 crank, makes it an externally balanced engine. A true PIA on a car as light as mine. 1st attempt at building this engine resulted in an engine that would have felt silky smooth in a 5000 lb truck, but too much vibration in the 1790 lb T. My current 383 stroker would probably feel like an electric motor in a truck, as smooth as it is now. The way you have described the results of your engine build, I have a good hunch your parts grinders know what they were doing. Little things like the bob weight, makes a big difference where its meat is removed. The pdf is really well written, considering it was penned by Harley engine builders. I've never been a fan of Harleys, but saying that could get me in more hot water.