Aaron,
Ed's given you a bum steer there. Probably all his playing with Fords lately
![Roll Eyes](http://fefcholden.org.au/forum/Smileys/default/rolleyes.gif)
Was your car originally fitted with amber indicators? If so, the wiring diagram in the workshop manual won't suit your car, and you'll need the FB utility/van version instead. Comparing these two shows you exactly what's what. Basically, the set-up that makes the dual purpose blinker/brake lights work is also what makes the dual purpose blinker/reversing light function.
This has been discussed recently, in
this thread, which includes the FB wiring diagram.
cheers
RET