ok with it doing what you say its doing there is either a misfire from the engine causing this OR what is happening is the torque converter is slipping in and out of lock up ( most common problem ) to know if it IS the convertor causing this problem the car needs to be driven with a scan tool connected and with the tool threw the computer with the tool lock up the converter and see what the transmission slip speed is reading if its bouncing from say like 20 RPM to 200 -300 RPM back and forth as you are feeling this then either there is a valve body problem or more than likey the convertor is bad.if the slip speed is good and stays under say like 50 RPM and stays there and you still feel it with the scan tool you need to monitor engine misfires and see if any of the cylinders are showing a current misfire when its acting up if so then there could be a bad plug wire or spark plug causing this problem

it may help for a little while.its hit or miss with the Lucas.give it a shot it comes down to how far the clutches are work inside the convertor.you got nothing to loose right?