If I remember correctly Eagle cast 4 in cranks have a target bobweight of 1850 grams. They have been made that way for a couple years so it could be neutral balanced. If your rods/pistons/rings/bearings didnt work out to more than 1850, neutral balancing would have taken the least effort and cost to balance. If it were me that is what I would try next. Swap the half moon flexplate for a std one and damper also if the current one is not a neutral damper.