I am very grateful to Norman Lutz for his “gearsets” information - shown below.
I’ve also made up a table of the gear tooth counts (as far as I could reckon).
There are a couple of missing gearbox prefixes-
KGN - overdrive 4.2 XJ6 - 2.933 first (essentially the same as KFN)
KPN - overdrive 3.4 and 4.2 Series 2 XJ6 (after engine 8L22647) - 3.238 first
KB - 3.238 first (essentially the same as KM) - probably XJS
Note that the tooth count on the cluster/ mainshaft is the same for 2nd and 3rd in all four ratio types.