Convert floor ship to Automatic

Thanks for the response I had a long talk with my Grandson and we have decided to convert to maybe a mild 360 with a 4 speed and dual exhaust. I did convert the 66 Dart to 3 on the floor `with a floor hump from a 66 Cuda fit like a glove. It had a column shift and i could not get to shift right. Again thanks for the much needed advise.