The distance between the face of the brake drum and the face of the rim is not the same for all half width hub Huntmasters as some were fitted with 20" wheels in 1954 whereas 19" wheels were the norm in 1955. 20" wheels used a WM1 rim whereas 19" wheels used a WM2 rim. Hence the different measurements.
One of these days, when I get round to it, I will write an article for Cheval de Fer including a table of these measurements, but getting the table correct is somewhat fraught.
Roger's advice, which is the same as that from the Ariel Works Service Manager, CW Waller, is sound.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.