1957 Roadmaster Dyna-flow torque converter


I have the engine running perfectly, re-built carburetor, electronic ignition, new plugs and wires, new rotor, new distributor cap, new vacuum advance (should have just bought a new distributor) had everything checked out by a master mechanic.
in "park" engine revs up perfectly, advance operates as it should....
.....However, when accelerating on the road, car is sluggish (I know "Dynoslush") but, the car is sluggish, seems to be struggling and there is a vibration until speed is achieved then it motors along smoothly, until you stomp on it. Then vibration is back until speed is achieved again.

Does anyone else think this is/could be, the torque converter???

The 1957 tech rep listed in the BCA Bugle told me that the 57 doesn't really have a torque converter.....more confusion!!

Any comments would be greatly appreciated................before I tackle pulling the transmission out this winter.