You will receive lots of arguments both ways (electric vs mechanical pump) and advice on safety features to add if you go with the electric pump. I will let others elaborate on those points.
The factory location for an electric pump on carbureted cars was on a bracket attached to the rear subframe below the left-hand fuel tank. The pump had an unfused connection to the ignition switch for 12V power. The pump earth wire was connected to the car's chassis/body. (This is where others will advise you on modern safety features to add to the basic installation). Some people also don't like the pump on the subframe and mount them on the seat back inside the boot. Location is obviously your decision to make.
The most important thing in pump selection (if you are running SU carbs) is pressure. Select a pump that delivers about 2 to 3 PSI. You can use a higher pressure pump but a pump that delivers more than 3 PSI will require a fuel pressure regulator before the carbs to prevent overpowering the float valves. The most common aftermarket electric pumps are from Facet. Their rectangular "brick" pumps are inexpensive but noisy. They can be mounted on rubber pads or bushings to quiet them a bit. Facet also has interrupter pumps that are sometimes referred to as "silver top" or "gold top" pumps. These are more sophisticated pumps and they are a bit quieter. They also cost more.
Almost any pump meeting the pressure requirements will be fine. Almost any pump you find will supply more fuel (gallons per minute) than the Mini requires.
