I am pretty sure I saw the diagrams on roverpars.com or roversnorth, you need to view it with mozilla, but it had them at least so you could look at them...
Circuit Diagram, 2.25ltr Petrol, Series IIA, Positive Earth p83
Circuit Diagram, 2.25ltr Petrol, Series IIA, Negative Earth to
US Federal Standards p84
Circuit Diagram, 2.25ltr & 2.6ltr Petrol, Series III,
Negative Earth p85
the guys on the phone said it should be the same as the series III