Main jet size 1065 was "standard" but not marked on military parts (see also mysterious parts page). Main jet 170 was originally applied according to specification of 1937.
Slide should have 6/4 cut away and needle position 3 (counted from top). As from 3/11/1941, needle position changed to 2. Possibly to cater for the lesser pool petrol quality.
These are the original AMAL factory settings for WD16H.
Due to wear, age and modern petrol, things might need some tweeking for the best performance.