MG Car Repair: 76 MG Positive Earthed, mg midget, negative earth

Question
I have a 76 MG Midget that was a barn find and the vehicle was hooked up as Positive earthed.  After looking at the wiring diagram, I am under the impression that this vehicle model is supposed to be negative earthed.  Please let me know if the vehicle should be negative earthed and what issues could I come across because of it being hooked up as positive earthed.  I am having issues with no spark which lead to me investigating the coil and wiring diagram.  The vehicle will turn over from the starter and many of the electrical components will function.  Thanks in advance.

Answer
Yes, a 76 Midget should definitely be wired for negative earth.  
There could be damage to the alternator, and if the fuel pump has a diode inside the lid, then this could have burnt out the pump.  I have seen such pumps with the black plastic lid melted by the heat.  
Most radios don't like reverse voltage.

Wipers, heater & screenwash motors will all turn the wrong way, but it won't do them any damage.  Lamps will be fine.

Connect the battery correctly and turn on the ignition, but do not try to start the car.  If the fuel pump ticks and the red ignition light comes on, then just MAYBE you have got away with it.