The Paul Goff kit will fit on a 56-59 Ariel fork with very little issue, and the two way damping works extremely well when the air gap is set correctly.
I can imagine that with a little machining work you could persuade the kit to fit the earlier forks. The main issue is that they come threaded for the larger diameter, where the earlier forks have the fork top nut adapter to fit the smaller top nut through the earlier top yoke.
My guess is that you would have to make a set of smaller top nuts with a thread on the inside for the compression dampers.
You might need to measure to make sure the height is correct, because that will massively affect the damping if it is too high/low.
It is MUCH easier to get the air gap right when you have the drain screws at the bottom of the sliders!
Of course, if you just want the progressive springs, they are a straight swap.
AOMCC Member Number 4068
1957 Ariel VH
1956 Ariel KH (LARGE project!)