The earlier iron clad Torqueflite A-466 used on the 407 and 408 Mk1 had kickdown just the same as the 411 with the A-727 Torqueflite, (the description of the kickdown function is exactly the same in the 411 Owners Manual).
Below 29mph from either 2 or D(3) it will kickdown to 1st. Between 29-60 mph it will shift from D to 2.
In both cases kickdown is actuated by pressing the accelerator pedal to the floor stop.
I don't believe any of the V8 cars up to and including the 411 had part throttle kickdown (PTK).
It appears from
this thread on a Mopar forum that PTK was introduced in 1971 for the A-727. The A-904 Torqueflite had PTK from 1967, but I don't think Bristol used the A-904.
It's also clear that PTK requires a different transmission valve body, so any talk of Bristol deleting PTK is yet another Bristol myth.