Hello Guss
There is a lot of information about maintenance in the hand book, see action magazine if you want to order.
There were three different options of gearbox, ratios below.
Top. Third. Second. First.
Synchromesh ... 4.66 : 1. 6.25 : 1. 9.85 : 1. 16.8 : 1
Sports. ... 4.66 : 1. 6.4. ; 1. 9.3. : 1. 17.7 : 1
Competition
Sports. ... 4.25 : 1. 5.82 : 1. 8.98 : 1. 15.3 : 1
I would imagine that the ratios quoted are through the differential but sadly I don’t have that information. It is commonplace for top gear to be 1 : 1 in the gearbox.
I can’t see anything to indicate what the 22CH would reference.