MG Car Repair: 78 MGB wiring for od switch, switch wiring, fuel pump

Question
the switch and wiring were removed from car when purchased. Seller claims OD works. Cannot find any information for switch wiring -can you help?

Answer
Hi Tammy,
The manual on/off switch got it's power from the fuel pump circuit but you can power it from any Ignition-on circuit. Then from the  on/off switch to the transmission "3rd/4th" only switch to the OD solenoid. That's all there was to it. The OD was not operated in 1st or reverse. First gear was of no use for OD and reverse would destroy the OD if activated in reverse as it could not be operated backwards.
Howard