I can't think of any reason driving the pump off the diff would have any advantage. And the disadvantages are numerous. The engines oil pressure/volume requirements vary with engine speed, not vehicle speed.de
Gordon, using the stock pump to fill a reservoir which then feeds an external pump is interesting. And I don't see how it would constitute an illegal dry sump. The sump is still very much wet! But if the stock Alfa pump is adequate to keep the reservoir filled, I wonder why the need for an external pump? On average, the external pump would be limited to providing the same volume of oil delivered by the stock pump, otherwise the reservoir would drain and the sump would overfill. Was this regulated somehow in the application you saw?
'66 GTV racecar, '71 Spider racecar, '74 GTV street car, '71 GTV project