1974 Dodge Dart Magnum Swap

Where did you get this engine; from a truck you were able to drive and test, or did you get it already removed? I see you said it's the balancer and flex plate that came on the engine, but I am wondering if they gave you a mismatched flex plate, or balancer. Some of the descriptions are conflicting, making it harder to evaluate. It shakes at highway speeds, but not sitting in park with rpm at a steady 2500, and goes away when engine is turned off while at speed. At what vehicle speed and rpm does it actually show up? Is it worse when you floor it while it's happening? Do you feel it at all in second gear, before transmission shifts to third? Also, an early post said you were using a new converter, but a recent post said it was from your existing trans, so what's the story there? Sorry for all questions in one post.