I wouldn't bother hunting for the series EMER WHEELED VEHICLES Q 020-029 as they are just general & cover a wide range of Rover Mks & as such there is no ambulance coverage. The complete sequence spreads over four A4 binders. They are somewhat illogical in their layout. They are a mish-mash of Rover publications & devoid of some useful information although some is also covered in EMER POWER.
A suffix defines a precise variant. Thus EMER WHEELED VEHICLES:
Q 020/7 - Q 029/7 covers Ambulance, 2/4 Stretcher, Rover 7
After re-designation of Rover EMERs in 1969 became:
Q 020/2 - Q 029/2 covers Ambulance, 2/4 Stretcher, Rover 9 & 11
Q 020/17 - Q 029/17 covers Ambulance, 2/4 Stretcher, Rover Series 3