New Petrol Pumps for a Diesel to Petrol Conversion

Hi I have purchased a 1983 Patrol which has been converted to the 4.5 Petrol engine. The vehicle broke down as the electrical feed to the petrol pumps failed. I determined that it has 2 pumps mounted near the left back wheel near the petrol tank. These I presume were still the original diesel pumps. They were mounted standing upright (vertical). I have now purchased 2 racing fuel pumps. Questions - why did the patrol have 2 pumps? Is it for redundancy or do they both pump at the same time? Can I move the pumps to the engine bay rather and mount them horizontally? This would make the wiring much shorter and less prone to failure. Do I mount the pumps in serial or in parallel? Do I fit individual pump switches for each pump on the dash? (I fitted an electrical pump to my Beetle and wired an on/off switch for the pump on the dash). I have a Dictator engine management system - do I wire the pumps into it? Thank you very much and greetings from South Africa.