Hi mate,
The adjustable rams were on early models, sorry for confusion there. Now, I have a schematic diagram of a Mk2 steering circuit, not sure if it is identical to a Mk3, too long ago since working on them. It has Orbitrol unit. To my mind Mk2 diagram suggests it is a spool valve with one selector control, and I recall it was a simpler set up than the Mk1.
on a Mk2, for interest;
Pressure relief valve, non adjustable and set at 1750psi
No idea about a manual, the army workshop manual was in the EMER system, but as the machine was also sold in civilian market, might be worth advertising in the Plant & Machinery magazine.