I have a 1972 Nova 350 auto. that is totally stock right down to the smog pump. I recently installed new plugs. new wires, converted the distributor from points to electronic & had the transmission serviced. All of this was done about the same time. Now while cruising on the highway I have a surging problem. The timing checks out ok as does the timing advance. I did notice today that the transmission is overfull. Any ideas?