I believe that '53 has a one year only bell housing for
the Powerflite that allows it to be mated to the same
engine as the Fluid-Torque trans. '54 has the newer
style bell housing that is PF only. I've driven '53s
with both trans, and I think the Fluid-Torque is quicker
than the Powerflite, even left in high range.
My '54 is slow off the line, but her rear end is a 2.93
instead of the original 3.54, so she's built for
cruising, not street racing.
Cheers,
Roger