FWH needed different sliders for the bigger axle, the mudguard mountings were changed at the same time. From memory (without checking spares books numbers) the longer bushes and slightly different damping hole pattern was in use from '55 and before that the shorter bushes were used (with the slightly different damping hole arrangement in the stanchions).
As Adrie says in '55 the lower yoke gained a mounting for the steering lock (but it doesn't stop the steering working if you mix those up).
I think the bushes (long/short) might be what governs the damping (although even there a mis-match might not be 'fatal') and they are interchangeable so at a (hopefully) educated guess you can use components across the '55/'56 split to match to the correct sliders for whichever front hub you need to use.
(There are some articles about that deal with the front fork changes - and modifications - in detail....)
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)