Which wiring we are talking about here?
Wiring for power and for speakers will most probably be straight forward replacement, however power side needs to be inspected if exactly the same.
Clock/display on the dash will be of no use, only clock side will work.
I checked connections of R770 and CD32 and here are the differences.
Pictures shown are connectors on radio side.
D connector from R700 will be left dangling in the back as you do not have where to connect it on CD32. This connector is responsible for feeding display side of Clock/Display on the dash. Only clock will be working.
B connector from R770 is straight swap to CD32
A connector from R770 has white and pink wires at positions Pin2 and Pin 3 respectively. These two wires are responsible for remite controls.
White and Pink wires needs to be connected to CD32 connector C on pins 11 and 12 (white on pin11 and pink on pin 12). The rest of A connector from R770 is straight swap to CD32 A connector.
Now there is one big difference to mention. Two versions of steering wheel controls exist (mk1 and mk2) and they are not connected to Rover model versions. You cannot tell from outside which version you have. However these two version differ in resistance values given when each button on steering wheel controls are pressed. R770 uses mk1 veraion of steering wheel controls, while CD32 uses mk2 versio , as far as I know.
This means your steerig wheels controls will not work correctly on CD32. You can try and see. Only way for them to work correctly is to swap steering wheel controls for mk2 version.