Well the official answer is, it depends on what version and how much you are carrying. there are 5 different tyre pressures given in the servicing schedule.
A - 35psi front and rear for road, 35psi front and rear off road.
B - 35 front 45 rear for road, 35 front and rear off road.
C - 35 front 50 rear for road, 35 front 40 rear off road.
D - 35 front 55 rear for road, 35 front 45 rear off road.
E - 35 front 70 rear for road, 35 front 55 rear off road.
The schedule lists 29 different versions of K9 to which the five different type pressure code apply.
Common ones are
Truck, G.S., 1 Ton 4x4 Austin K9 A
Truck, G.S., F.F.R. 1 Ton 4x4 Austin K9, Mk 2 A
Radio station, Truck mounted, 1 Ton 4x4 Austin K9 Mk2 A
Radio station, Truck mounted, SRC42/C45HP, 1 Ton 4x4 Austin K9 D
Radio station, Truck mounted, SRD11/R234, 1 Ton 4x4 Austin K9 C
Truck, Tanker, Water, 1 ton, 200 gal., Austin K9 B
I have a C42 and a WS19 fitted in mine and a lot of other kit gets carried in the back as well going to shows so I run on code D, seems to work ok.
PT